Acute unilateral pulmonary edema is an unusual clinical condition occasionally associated with severe mitral valve insufficiency. We describe a patient diagnosed as having unilateral pulmonary edema after an acute anterior myocardial infarction. Echocardiograms performed in the acute phase ruled out mitral insufficiency. A perfusion lung scan showed left-sided pulmonary hypoperfusion. The diagnosis of acquired hypoplasia of the left pulmonary artery tree was made by chest computed tomography. The pathogenesis and differential diagnosis are discussed.