Actually, the problem occurs when I load the panel. The activeX control is alone in my child panel and when I load the panel, the focus is automaticaly set on the first control of the panel. And then the focus rectangle appears around my control (even if I set the ShowFocusMode property to "0-cwShowFocusNone"). So I set an other panel to be the active panel just after displaying this child panel in order to avoid this behaviour, and it works.