diff --git a/reactos/iface/addsys/w32ksvc.db b/reactos/iface/addsys/w32ksvc.db
index 05a153c42c8..44e6b9782e3 100644
--- a/reactos/iface/addsys/w32ksvc.db
+++ b/reactos/iface/addsys/w32ksvc.db
@@ -545,3 +545,4 @@ NtUserYieldTask                         0
 NtUserGetDesktopWindow			0
 # ReactOS only system calls
 NtUserAcquireOrReleaseInputOwnership    1
+NtUserGetWindowThreadProcessId          2
diff --git a/reactos/include/win32k/ntuser.h b/reactos/include/win32k/ntuser.h
index ae329a63c7c..32f218d476b 100644
--- a/reactos/include/win32k/ntuser.h
+++ b/reactos/include/win32k/ntuser.h
@@ -1741,6 +1741,9 @@ DWORD
 STDCALL
 NtUserYieldTask(VOID);
 
+DWORD STDCALL
+NtUserGetWindowThreadProcessId(HWND hWnd, LPDWORD UnsafePid);
+
 #endif /* __WIN32K_NTUSER_H */
 
 /* EOF */
diff --git a/reactos/subsys/win32k/include/window.h b/reactos/subsys/win32k/include/window.h
index d75adbf84e6..f54f5e49d9f 100644
--- a/reactos/subsys/win32k/include/window.h
+++ b/reactos/subsys/win32k/include/window.h
@@ -83,6 +83,7 @@ typedef struct _WINDOW_OBJECT
   PSCROLLBARINFO wExtra;
   LONG UserData;
   WNDPROC WndProc;
+  PETHREAD OwnerThread;
 } WINDOW_OBJECT, *PWINDOW_OBJECT;
 
 /* Window flags. */
@@ -108,6 +109,10 @@ BOOL     FASTCALL W32kIsChildWindow (HWND Parent, HWND Child);
 HWND     FASTCALL W32kGetDesktopWindow (VOID);
 HWND     FASTCALL W32kGetFocusWindow (VOID);
 HWND     FASTCALL W32kSetFocusWindow (HWND hWnd);
+
+DWORD FASTCALL
+W32kGetWindowThreadProcessId(PWINDOW_OBJECT Wnd, PDWORD pid);
+
 #endif /* __WIN32K_WINDOW_H */
 
 /* EOF */
diff --git a/reactos/subsys/win32k/ntuser/window.c b/reactos/subsys/win32k/ntuser/window.c
index 73c2ca8ce8a..f834d00ccdf 100644
--- a/reactos/subsys/win32k/ntuser/window.c
+++ b/reactos/subsys/win32k/ntuser/window.c
@@ -16,7 +16,7 @@
  *  along with this program; if not, write to the Free Software
  *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
-/* $Id: window.c,v 1.66 2003/07/24 15:59:34 rcampbell Exp $
+/* $Id: window.c,v 1.67 2003/07/25 19:35:51 gdalsnes Exp $
  *
  * COPYRIGHT:        See COPYING in the top level directory
  * PROJECT:          ReactOS kernel
@@ -490,6 +490,7 @@ W32kCreateDesktopWindow(PWINSTATION_OBJECT WindowStation,
   WindowObject->ClientRect = WindowObject->WindowRect;
   WindowObject->UserData = 0;
   WindowObject->WndProc = DesktopClass->Class.lpfnWndProc;
+  WindowObject->OwnerThread = PsGetCurrentThread();
 
   InitializeListHead(&WindowObject->ChildrenListHead);
   ExInitializeFastMutex(&WindowObject->ChildrenListLock);
@@ -631,6 +632,7 @@ NtUserCreateWindowEx(DWORD dwExStyle,
   WindowObject->Parent = ParentWindow;
   WindowObject->UserData = 0;
   WindowObject->WndProc = ClassObject->Class.lpfnWndProc;
+  WindowObject->OwnerThread = PsGetCurrentThread();
 
   ExAcquireFastMutexUnsafe(&ParentWindow->ChildrenListLock);
   InsertHeadList(&ParentWindow->ChildrenListHead,
@@ -1964,4 +1966,36 @@ NtUserGetDesktopWindow()
 	return W32kGetDesktopWindow();
 }
 
+
+DWORD FASTCALL
+W32kGetWindowThreadProcessId(PWINDOW_OBJECT Wnd, PDWORD pid)
+{
+   if (pid) *pid = (DWORD) Wnd->OwnerThread->Cid.UniqueThread;
+   return (DWORD) Wnd->OwnerThread->ThreadsProcess->UniqueProcessId;
+}
+
+
+DWORD STDCALL
+NtUserGetWindowThreadProcessId(HWND hWnd, LPDWORD UnsafePid)
+{
+   PWINDOW_OBJECT Wnd;
+   DWORD tid, pid;
+
+   //W32kAcquireWindowsLockShared();
+
+   if (!(Wnd = W32kGetWindowObject(hWnd)))
+   {
+      SetLastWin32Error(ERROR_INVALID_WINDOW_HANDLE);
+      return 0;
+   }
+
+   tid = W32kGetWindowThreadProcessId(Wnd, &pid);
+   W32kReleaseWindowObject(Wnd);
+   //W32kReleaseWindowsLock();
+   
+   if (UnsafePid) MmCopyToCaller(UnsafePid, &pid, sizeof(DWORD));
+   
+   return tid;
+}
+
 /* EOF */