Bronchial adenoma,especially adenocystic carcinoma [cylindroma] of the tracheobronchial tree is relatlvely rare in incidence. This is the report of one case of cylindroma in a 28 year old female,surgically treated at the Deparment of Thoracic Surgery,Seoul National University Hospital. The tumor was located at the left main bronchus and completely obstructing the bronchial lumen.Left pneumonecromy was performed because of the irreversible bronchiectatic and fibrotic changes of the entire left lung.