We present a rare complication after partial cavo-pulmonary connection in a case of complex congenital heart disease (tricuspid atresia, double outlet right ventricle, total abnormal pulmonary venous drainage, persistent left superior vena cava). After one a half ventricular repair, a superior vena cava syndrome developed, because of increased pulmonary pressure. Additional, a stenosis at the level of anastomosis between the left superior vena cava and the left pulmonary arterial branch could be demonstrated. The evolution was rapid with neurological deterioration, and despite the intensive medical treatment, the child died. The clinical course and the therapeutic possibilities are discussed, as well as the controversial role of additional pulmonary blood flow.