Congenital Cystic Adenomatoid Malformation [C.C.A.M], one of lung bud anomalies, is an unusual lesion, only about 200 cases baring been reported by 1980, and characterized by marked proliferation of terminal respiratory structures. Recently we experienced two infants with C.C.A,M., whose clinical courses were quite different. On case 1, the patient was 25-day-old female, and suffered from progressive respiratory distress for 10 days duration. A right middle lobectomy was performed, with a satisfactory postoperative course. On case II, the patient was 7omonth-old male, and admitted for evaluation of known pulmonary anomaly, which was detected for the first time during hospitalization for treatment of pneumonia at 1 month of his age. He underwent a lingular segmentectomy, but died of respiratory insufficiency on postop 10th day. We believe that awareness of the presence of C.C.A.M. is important in making the differential diagnosis of progressive respiratory disease or of recurrent pulmonary infection in infants.