Unilateral adsence of a pulmonary artery is frequently undiagnosed. Unless this entity is recognized, a patient with a potentially curable lesion may become inoperable. The importance of considering unilateral absence of a pulmonary artery in the diffirential diagnosis of cyanotic congenital heart disease and pulmonary hypertension has become clear. We exeperienced a case of congenital isolated unilateral absence of it. pulmonary artery confirmed by clinical features, lung scan, echocardiogram and angiogram.