diff --git a/reactos/dll/win32/advapi32/sec/lsa.c b/reactos/dll/win32/advapi32/sec/lsa.c
index 4a89b0f0753..90a257b8a60 100644
--- a/reactos/dll/win32/advapi32/sec/lsa.c
+++ b/reactos/dll/win32/advapi32/sec/lsa.c
@@ -348,47 +348,47 @@ LsaFreeMemory(PVOID Buffer)
  */
 NTSTATUS
 WINAPI
-LsaLookupNames(
-    LSA_HANDLE PolicyHandle,
-    ULONG Count,
-    PLSA_UNICODE_STRING Names,
-    PLSA_REFERENCED_DOMAIN_LIST *ReferencedDomains,
-    PLSA_TRANSLATED_SID *Sids)
+LsaLookupNames(IN LSA_HANDLE PolicyHandle,
+               IN ULONG Count,
+               IN PLSA_UNICODE_STRING Names,
+               OUT PLSA_REFERENCED_DOMAIN_LIST *ReferencedDomains,
+               OUT PLSA_TRANSLATED_SID *Sids)
 {
-    PLSA_TRANSLATED_SID2 Sids2;
-    LSA_TRANSLATED_SID *TranslatedSids;
-    ULONG i;
+    LSAPR_TRANSLATED_SIDS TranslatedSids;
+    ULONG MappedCount = 0;
     NTSTATUS Status;
 
     TRACE("(%p,0x%08x,%p,%p,%p)\n", PolicyHandle, Count, Names,
           ReferencedDomains, Sids);
 
-    /* Call LsaLookupNames2, which supersedes this function */
-    Status = LsaLookupNames2(PolicyHandle, Count, 0, Names, ReferencedDomains, &Sids2);
-    if (!NT_SUCCESS(Status))
-        return Status;
+    RpcTryExcept
+    {
+        *ReferencedDomains = NULL;
+        *Sids = NULL;
 
-    /* Translate the returned structure */
-    TranslatedSids = RtlAllocateHeap(RtlGetProcessHeap(), 0, Count * sizeof(LSA_TRANSLATED_SID));
-    if (!TranslatedSids)
-    {
-        LsaFreeMemory(Sids2);
-        return SCESTATUS_NOT_ENOUGH_RESOURCE;
+        TranslatedSids.Entries = Count;
+        TranslatedSids.Sids = *Sids;
+
+        Status = LsarLookupNames((LSAPR_HANDLE)PolicyHandle,
+                                 Count,
+                                 (PRPC_UNICODE_STRING)Names,
+                                 (PLSAPR_REFERENCED_DOMAIN_LIST *)ReferencedDomains,
+                                 &TranslatedSids,
+                                 LsapLookupWksta,
+                                 &MappedCount);
+
+        *Sids = (PLSA_TRANSLATED_SID)TranslatedSids.Sids;
     }
-    RtlZeroMemory(Sids, Count * sizeof(PLSA_TRANSLATED_SID));
-    for (i = 0; i < Count; i++)
+    RpcExcept(EXCEPTION_EXECUTE_HANDLER)
     {
-        TranslatedSids[i].Use = Sids2[i].Use;
-        if (Sids2[i].Use != SidTypeInvalid && Sids2[i].Use != SidTypeUnknown)
+        if (TranslatedSids.Sids != NULL)
         {
-            TranslatedSids[i].DomainIndex = Sids2[i].DomainIndex;
-            if (Sids2[i].Use != SidTypeDomain)
-                TranslatedSids[i].RelativeId = *GetSidSubAuthority(Sids2[i].Sid, 0);
+            MIDL_user_free(TranslatedSids.Sids);
         }
-    }
-    LsaFreeMemory(Sids2);
 
-    *Sids = TranslatedSids;
+        Status = I_RpcMapWin32Status(RpcExceptionCode());
+    }
+    RpcEndExcept;
 
     return Status;
 }
@@ -487,12 +487,11 @@ LsaLookupPrivilegeValue(IN LSA_HANDLE PolicyHandle,
  */
 NTSTATUS
 WINAPI
-LsaLookupSids(
-    LSA_HANDLE PolicyHandle,
-    ULONG Count,
-    PSID *Sids,
-    PLSA_REFERENCED_DOMAIN_LIST *ReferencedDomains,
-    PLSA_TRANSLATED_NAME *Names)
+LsaLookupSids(IN LSA_HANDLE PolicyHandle,
+              IN ULONG Count,
+              IN PSID *Sids,
+              OUT PLSA_REFERENCED_DOMAIN_LIST *ReferencedDomains,
+              OUT PLSA_TRANSLATED_NAME *Names)
 {
     LSAPR_SID_ENUM_BUFFER SidEnumBuffer;
     LSAPR_TRANSLATED_NAMES TranslatedNames;
diff --git a/reactos/dll/win32/advapi32/sec/misc.c b/reactos/dll/win32/advapi32/sec/misc.c
index 154ad8a84f2..f8a6ef05aa3 100644
--- a/reactos/dll/win32/advapi32/sec/misc.c
+++ b/reactos/dll/win32/advapi32/sec/misc.c
@@ -1177,7 +1177,7 @@ LookupAccountNameA(LPCSTR SystemName,
 /******************************************************************************
  * LookupAccountNameW [ADVAPI32.@]
  *
- * @unimplemented
+ * @implemented
  */
 BOOL
 WINAPI
@@ -1189,78 +1189,94 @@ LookupAccountNameW(LPCWSTR lpSystemName,
                    LPDWORD cchReferencedDomainName,
                    PSID_NAME_USE peUse)
 {
-    /* Default implementation: Always return a default SID */
-    SID_IDENTIFIER_AUTHORITY identifierAuthority = {SECURITY_NT_AUTHORITY};
-    BOOL ret;
-    PSID pSid;
-    static const WCHAR dm[] = {'D','O','M','A','I','N',0};
-    unsigned int i;
+    OBJECT_ATTRIBUTES ObjectAttributes = {0};
+    UNICODE_STRING SystemName;
+    UNICODE_STRING AccountName;
+    LSA_HANDLE PolicyHandle = NULL;
+    PLSA_REFERENCED_DOMAIN_LIST ReferencedDomains = NULL;
+    PLSA_TRANSLATED_SID TranslatedSid = NULL;
+    PSID pDomainSid;
+    DWORD dwDomainNameLength;
+    DWORD dwSidLength;
+    UCHAR nSubAuthorities;
+    BOOL bResult;
+    NTSTATUS Status;
 
-    TRACE("%s %s %p %p %p %p %p - stub\n", lpSystemName, lpAccountName,
+    TRACE("%s %s %p %p %p %p %p\n", lpSystemName, lpAccountName,
           Sid, cbSid, ReferencedDomainName, cchReferencedDomainName, peUse);
 
-    if (!ADVAPI_IsLocalComputer(lpSystemName))
+    RtlInitUnicodeString(&SystemName,
+                         lpSystemName);
+
+    Status = LsaOpenPolicy(lpSystemName ? &SystemName : NULL,
+                           &ObjectAttributes,
+                           POLICY_LOOKUP_NAMES,
+                           &PolicyHandle);
+    if (!NT_SUCCESS(Status))
     {
-        SetLastError(RPC_S_SERVER_UNAVAILABLE);
+        SetLastError(LsaNtStatusToWinError(Status));
         return FALSE;
     }
 
-    for (i = 0; i < (sizeof(ACCOUNT_SIDS) / sizeof(ACCOUNT_SIDS[0])); i++)
+    RtlInitUnicodeString(&AccountName,
+                         lpAccountName);
+
+    Status = LsaLookupNames(PolicyHandle,
+                            1,
+                            &AccountName,
+                            &ReferencedDomains,
+                            &TranslatedSid);
+
+    LsaClose(PolicyHandle);
+
+    if (!NT_SUCCESS(Status) || Status == STATUS_SOME_NOT_MAPPED)
     {
-        if (!wcscmp(lpAccountName, ACCOUNT_SIDS[i].account))
-        {
-            if (*cchReferencedDomainName)
-                *ReferencedDomainName = '\0';
-            *cchReferencedDomainName = 0;
-            *peUse = SidTypeWellKnownGroup;
-            return CreateWellKnownSid(ACCOUNT_SIDS[i].type, NULL, Sid, cbSid);
-        }
-    }
-
-    ret = AllocateAndInitializeSid(&identifierAuthority,
-        2,
-        SECURITY_BUILTIN_DOMAIN_RID,
-        DOMAIN_ALIAS_RID_ADMINS,
-        0, 0, 0, 0, 0, 0,
-        &pSid);
-
-    if (!ret)
-        return FALSE;
-
-    if (!RtlValidSid(pSid))
-    {
-        FreeSid(pSid);
-        return FALSE;
-    }
-
-    if (Sid != NULL && (*cbSid >= GetLengthSid(pSid)))
-        CopySid(*cbSid, Sid, pSid);
-
-    if (*cbSid < GetLengthSid(pSid))
-    {
-        SetLastError(ERROR_INSUFFICIENT_BUFFER);
-        ret = FALSE;
-    }
-
-    *cbSid = GetLengthSid(pSid);
-
-    if (ReferencedDomainName != NULL && (*cchReferencedDomainName > wcslen(dm)))
-        wcscpy(ReferencedDomainName, dm);
-
-    if ((*cchReferencedDomainName <= wcslen(dm)) || (!ret))
-    {
-        SetLastError(ERROR_INSUFFICIENT_BUFFER);
-        ret = FALSE;
-        *cchReferencedDomainName = wcslen(dm) + 1;
+        SetLastError(LsaNtStatusToWinError(Status));
+        bResult = FALSE;
     }
     else
     {
-        *cchReferencedDomainName = wcslen(dm);
+        pDomainSid = ReferencedDomains->Domains[TranslatedSid->DomainIndex].Sid;
+        nSubAuthorities = *GetSidSubAuthorityCount(pDomainSid);
+        dwSidLength = GetSidLengthRequired(nSubAuthorities + 1);
+
+        dwDomainNameLength = ReferencedDomains->Domains->Name.Length / sizeof(WCHAR);
+
+        if (*cbSid < dwSidLength ||
+            *cchReferencedDomainName < dwDomainNameLength + 1)
+        {
+            *cbSid = dwSidLength;
+            *cchReferencedDomainName = dwDomainNameLength + 1;
+
+            bResult = FALSE;
+        }
+        else
+        {
+            CopySid(*cbSid, Sid, pDomainSid);
+            *GetSidSubAuthorityCount(Sid) = nSubAuthorities + 1;
+            *GetSidSubAuthority(Sid, (DWORD)nSubAuthorities) = TranslatedSid->RelativeId;
+
+            RtlCopyMemory(ReferencedDomainName, ReferencedDomains->Domains->Name.Buffer, dwDomainNameLength * sizeof(WCHAR));
+            ReferencedDomainName[dwDomainNameLength] = L'\0';
+
+            *cchReferencedDomainName = dwDomainNameLength;
+
+            *peUse = TranslatedSid->Use;
+
+            bResult = TRUE;
+        }
+
+        if (bResult == FALSE)
+            SetLastError(ERROR_INSUFFICIENT_BUFFER);
     }
 
-    FreeSid(pSid);
+    if (ReferencedDomains != NULL)
+        LsaFreeMemory(ReferencedDomains);
 
-    return ret;
+    if (TranslatedSid != NULL)
+        LsaFreeMemory(TranslatedSid);
+
+    return bResult;
 }
 
 
@@ -1499,11 +1515,11 @@ LookupPrivilegeNameW(LPCWSTR lpSystemName,
                                     &PrivilegeName);
     if (NT_SUCCESS(Status))
     {
-        if (PrivilegeName->Length + sizeof(WCHAR) > (*cchName) * sizeof(WCHAR))
+        if (PrivilegeName->Length + sizeof(WCHAR) > *cchName * sizeof(WCHAR))
         {
             Status = STATUS_BUFFER_TOO_SMALL;
 
-            (*cchName) = (PrivilegeName->Length + sizeof(WCHAR)) / sizeof(WCHAR);
+            *cchName = (PrivilegeName->Length + sizeof(WCHAR)) / sizeof(WCHAR);
         }
         else
         {
@@ -1512,7 +1528,7 @@ LookupPrivilegeNameW(LPCWSTR lpSystemName,
                           PrivilegeName->Length);
             lpName[PrivilegeName->Length / sizeof(WCHAR)] = 0;
 
-            (*cchName) = PrivilegeName->Length / sizeof(WCHAR);
+            *cchName = PrivilegeName->Length / sizeof(WCHAR);
         }
 
         LsaFreeMemory(PrivilegeName->Buffer);
diff --git a/reactos/dll/win32/lsasrv/lsarpc.c b/reactos/dll/win32/lsasrv/lsarpc.c
index acca2f6e77f..1a83d007f00 100644
--- a/reactos/dll/win32/lsasrv/lsarpc.c
+++ b/reactos/dll/win32/lsasrv/lsarpc.c
@@ -333,8 +333,91 @@ NTSTATUS LsarLookupNames(
     LSAP_LOOKUP_LEVEL LookupLevel,
     DWORD *MappedCount)
 {
-    UNIMPLEMENTED;
-    return STATUS_NOT_IMPLEMENTED;
+    SID_IDENTIFIER_AUTHORITY IdentifierAuthority = {SECURITY_NT_AUTHORITY};
+    static const UNICODE_STRING DomainName = RTL_CONSTANT_STRING(L"DOMAIN");
+    PLSAPR_REFERENCED_DOMAIN_LIST OutputDomains = NULL;
+    PLSA_TRANSLATED_SID OutputSids = NULL;
+    ULONG OutputSidsLength;
+    ULONG i;
+    PSID Sid;
+    ULONG SidLength;
+    NTSTATUS Status;
+
+    TRACE("LsarLookupNames(%p, %lu, %p, %p, %p, %d, %p)\n",
+          PolicyHandle, Count, Names, ReferencedDomains, TranslatedSids,
+          LookupLevel, MappedCount);
+
+    TranslatedSids->Entries = Count;
+    TranslatedSids->Sids = NULL;
+    *ReferencedDomains = NULL;
+
+    OutputSidsLength = Count * sizeof(LSA_TRANSLATED_SID);
+    OutputSids = MIDL_user_allocate(OutputSidsLength);
+    if (OutputSids == NULL)
+    {
+        return STATUS_INSUFFICIENT_RESOURCES;
+    }
+
+    RtlZeroMemory(OutputSids, OutputSidsLength);
+
+    OutputDomains = MIDL_user_allocate(sizeof(LSAPR_REFERENCED_DOMAIN_LIST));
+    if (OutputDomains == NULL)
+    {
+        MIDL_user_free(OutputSids);
+        return STATUS_INSUFFICIENT_RESOURCES;
+    }
+
+    OutputDomains->Entries = Count;
+    OutputDomains->Domains = MIDL_user_allocate(Count * sizeof(LSA_TRUST_INFORMATION));
+    if (OutputDomains->Domains == NULL)
+    {
+        MIDL_user_free(OutputDomains);
+        MIDL_user_free(OutputSids);
+        return STATUS_INSUFFICIENT_RESOURCES;
+    }
+
+    Status = RtlAllocateAndInitializeSid(&IdentifierAuthority,
+                                         2,
+                                         SECURITY_BUILTIN_DOMAIN_RID,
+                                         DOMAIN_ALIAS_RID_ADMINS,
+                                         0, 0, 0, 0, 0, 0,
+                                         &Sid);
+    if (!NT_SUCCESS(Status))
+    {
+        MIDL_user_free(OutputDomains->Domains);
+        MIDL_user_free(OutputDomains);
+        MIDL_user_free(OutputSids);
+        return Status;
+    }
+
+    SidLength = RtlLengthSid(Sid);
+
+    for (i = 0; i < Count; i++)
+    {
+        OutputDomains->Domains[i].Sid = MIDL_user_allocate(SidLength);
+        RtlCopyMemory(OutputDomains->Domains[i].Sid, Sid, SidLength);
+
+        OutputDomains->Domains[i].Name.Buffer = MIDL_user_allocate(DomainName.MaximumLength);
+        OutputDomains->Domains[i].Name.Length = DomainName.Length;
+        OutputDomains->Domains[i].Name.MaximumLength = DomainName.MaximumLength;
+        RtlCopyMemory(OutputDomains->Domains[i].Name.Buffer, DomainName.Buffer, DomainName.MaximumLength);
+    }
+
+    for (i = 0; i < Count; i++)
+    {
+        OutputSids[i].Use = SidTypeWellKnownGroup;
+        OutputSids[i].RelativeId = DOMAIN_ALIAS_RID_ADMINS;
+        OutputSids[i].DomainIndex = i;
+    }
+
+    *ReferencedDomains = OutputDomains;
+
+    *MappedCount = Count;
+
+    TranslatedSids->Entries = Count;
+    TranslatedSids->Sids = OutputSids;
+
+    return STATUS_SUCCESS;
 }