A 70-year-old man was admitted to our hospital because of cough and dyspnea. On the 7th hospital day, he suddenly suffered by severe pulmonary congestion and bilateral pleural effusion with a prominent heart murmur. After improvement of the symptoms, 3-D CT scan and cardiac catheterization confirmed patent ductal aneurysm of about 10.5cm in diameter. Because of pulmonary hemorrhage, an emergency operation was performed using a left thoracotomy approach. A large aneurysmal mass of about 12cm in diameter was transected and the pulmonary end and aortic end of the ductus arteriosus were closed using a patch under partial cardiopulmonary bypass. His postoperative course was uneventful and he was discharged on the 27th day after operation.