Digged thru Qt sources, found a solution for Vista:

Qt Code: 
  1. class CheckBoxStyleNoFocusDrawVista: public QWindowsVistaStyle{
  2. public:
  3. 	void drawControl(ControlElement element, const QStyleOption *opt,
  4. 	                               QPainter *p, const QWidget *widget) const
  5. 	{
  6. 	    switch (element) {
  7. 	    case CE_CheckBox:
  8. 	        if (const QStyleOptionButton *btn = qstyleoption_cast<const QStyleOptionButton *>(opt)) {
  9. 	            QStyleOptionButton subopt = *btn;
  10. 	            subopt.rect = subElementRect(SE_CheckBoxIndicator, btn, widget);
  11. 	            drawPrimitive(PE_IndicatorCheckBox, &subopt, p, widget);
  12. 	            subopt.rect = subElementRect(SE_CheckBoxContents, btn, widget);
  13. 	            drawControl(CE_CheckBoxLabel, &subopt, p, widget);
  14. 	        }
  15. 	        break;
  16. 	    default:
  17. 	    	QWindowsVistaStyle::drawControl(element, opt, p, widget);
  18. 	    }
  19. 	}
  20. };
  21.  
  22. void CheckBox1::CheckBox1():QCheckBox(){
  23. 	setStyle(new CheckBoxStyleNoFocusDraw());
  24. }
To copy to clipboard, switch view to plain text mode 

This needs to be extended for all operating systems (Windows, XP, Vista, Mac).