Thymic cyst is a relatively uncommon,usually asymptomatic benign lesion situated in the anterior mediastinum or in the neck,and sometimes in both regions. This is a report of two cases of congenital thymlc cyst in a 18 year old girl and a 43 tear old man. Those were treated with extirpation of the cystic lesion by thoracotomy successfully and had good postoperative results.