Unilateral absence of pulmonary artery or pulmonary artery agenesis (UAPA) is a rare congenital malformation that can present as an isolated lesion or in association with other cardiac anomalies. Though congenital, presentation in adults are also reported. Most common presentation in adults is of exercise intolerance. The developing lung on the affected side is hypoplastic. Diagnosis of UAPA is established by imaging methods like CT and MRI . There is no specific treatment for this condition. Treatment depends on patients symptomatology, presence of pulmonary hypertension and collateral circulation. Presence of pulmonary hypertension carries a bad prognosis. We present two adult patients with isolated left sided unilateral pulmonary artery agenesis with ipsilateral lung hypoplasia. The diagnosis was confirmed by CT chest and perfusion scan.