[[maeyanes]]

Hola...

Yo uso un procedimiento como este:

Código Delphi [-]
procedure ShowMDIChildForm(AFormClass: TFormClass);
var
  I: Integer;
  AForm: TForm;

begin
  for I := 0 to Pred(Application.MainForm.MDIChildCount) do
  begin
    AForm := Application.MainForm.MDIChildren[i];
    if AForm is AFormClass then
    begin
      if IsIconic(AForm.Handle) then
        ShowWindow(AForm.Handle, SW_RESTORE);
      AForm.BringToFront;
      Exit
    end
  end;
  AFormClass.Create(nil)
end;

Saludos...