Pulmonary sequestration is nonfunctional pulmonary tissue that does not communicate with the tracheobronchial tree and receives its blood supply from one or more anomalous systemic aeries. This abnormality originates during the embryonic period of lung development. It is classified as either extralobar or intralobar.Extralobar sequestration is a mass of pulmonary parenchyma anatomically separate from the normal lung, with a distinct pleural investment. Its blood supply is derived from the systemic circulation. The left side is involved in more than 90% of cases.Intralobar sequestration is an isolated segment of lung within the normal pleural investment that often receives blood from one or more aeries arising from the aoa or its branches. Intralobar sequestration is usually found within the lower lobes (98%), two-thirds are found on the left side.The diagnosis of intralobar sequestration may be established after repeated infections manifested by cough, fever, and consolidation in the posterior basal segment of the left lower lobe.