A 12 hour old newborn suffering from respiratory distress was found to have a well defined opaque mass in the right lung. The mass was well tolerated up the 33rd day of life when he developed acute respiratory distress, the upper respiratory tract being flooded with secretions. Chest X ray showed that the mass had disappeared and that there was a large cystic structure instead. A bronchogenic cyst was excised successfully from the right middle lobe. The early clinical manifestations of this bronchogenic cyst and the radiologic findings are discussed.