Pulmonary sequestration is an uncommon congenital pulmonary malformation characterized by presence of nonfunctioning lung tissue which receives its blood supply mostly from the anomalous systemic arteries - descending thoracic aorta or abdominal aorta, subclavian artery, innominated artery and internal mammary artery, etc. In our country, 39 cases were reported previously. The patient was a 40 years old woman and admitted due to productive cough for 1 year. The chest X-ray and chest C-T showed a dense mass containing a large cavity with air-fluid level and multiple radiolucent cysts in the right lower lung field. On the operative field, we could identify an aberrant large artery [ $phi$7mm which arose directly from the descending thoracic aorta at eighth thoracic spinal level and fed the sequestrated portion of the right lower lobe. The aberrant artery was double ligation after division. Only sequestrated lobe on the superolateral lesion of the right lower lobe was resected because of nonseparated lobes in all the right lobes. An abnormal vein and bronchiole were ligated with black silk. The patient`s postoperative course was unevenful.