The authors present a case-review of a 65 year-old female patient, hospitalized for rest dyspnoea and collaps condition, 3 weeks following her completed aorto-coronary by-pass. The symptoms were caused by a massive lung embolism. Upon the echocardiographic examination, a massive thrombus in the right-sided cardiac spaces--a rare complication of cardiosurgical procedures--was detected. The patient was treated surgically. At the present time, 4 months following the procedure, the patient is completely recovered.