Isolated unilateral absence of pulmonary artery is uncommon. Although not certain, genetic, teratogenic and mechanical factors are held responsible. The anomaly results from the involution of the proximal sixth aortic arch. In this report we present an asymptomatic 24 yrs old male patient. Unilateral right-sided absence of pulmonary artery was diagnosed by thoracic computerized tomography (CT) and angiographic evaluation.