A case of pericardial cyst appearing on chest X-ray finding of right hilar mass in 37 year old man is reported. He has been complaint of cough and substernal discomfort, on and off for 5 years. Thoracostomy revealed a fluid filled pericardial cyst of 6$ imes$5$ imes$3㎤ in size without communication with pericardial cavity, and confirmed as congenital pericardial cyst. Since the majority of pericardial cyst and diverticula are located in either cardiophrenic angle, the location at right hilum in this case is most unusual.