Unilateral Pulmonary artery agenesis (UPAA) is a rare congenital anomaly that is frequently associated with other cardiovascular anomalies such as tetralogy of fallot, right aortic arch, septal defects and PDA. Approximately 150 cases of UPAA have been reported. However, since many patients with isolated UPAA have a benign clinical course, the diagnosis may not be made until adulthood when an abnormal chest radiograph initiates a series of diagnostic tests. The patient who survives undetected to adulthood usually presents with an abnormal chest radiograph without concomitant cardiovascular abnormalities. Our purpose is to illustrate that a high index of suspicion is necessary to correctly diagnose these case.