Extralobar pulmonary sequestration, a rare form of bronchopulmonary sequestration, is a congenital anomaly in which a portion of nonfunctioning lung tissue is surrounded by its own pleura and is supplied by a systemic artery. We describe a case of extralobar pulmonary sequestration with unusual features. CT scanning of the chest demonstrated a non-enhancing, hyperdense mass within the right major fissure, and thoracotomy revealed that the mass received blood from a branch of the right pulmonary artery and drained into the left atrium. The pathologic diagnosis was extralobar pulmonary sequestration.