This example shows a creation of Message Dialog relative to center of Form1.
procedure TForm1.Button1Click(Sender: TObject); var MyForm: TForm; begin MyForm:=CreateMessageDialog('This is example', mtInformation, [mbOk]); with MyForm do begin Height:=130; Width:=150; Left:=Trunc((Form1.Width-Width)/2)+Form1.Left; Top:=Trunc((Form1.Height-Height)/2)+Form1.Top;; ShowModal; end; end;