Having read MSDN I concluded that this is how GetWindowTheme() should be from the documentation. My overall aim is to find if there is a "Theme" on the Control, in the example provided its a Button. I have looked through WinAPIEx.au3 (GetWindowTheme isn't there) with Results for _WinAPI_GetThemeAppProperties() & _WinAPI_GetThemeInt() (plus more) which I can't see applying to what I want. Therefore does anyone know if it's possible to determine whether a "Theme" has been applied to a Control