Unilateral absence of a pulmonary artery is an uncommon anomaly, which presents as an isolated lesion or in combination with other congenital heart disease such as TOF or PD^. We encountered three cases of isolated unilateral absence of a pulmonary artery;one was left pulmonary artery agenesis with right sided aortic arch and the others were right pulmonary artery agenesis with left sided aortic arch. Plain chest radiograph showed considerable loss of unilateal lung volume and lack of ipsilateral hilar shadow. Pulmonary angiogram which was done in two cases, revealed proximal interruption of a pulmonary artery. Chest CT was done in only one case, on which right pulmonary artery was absent and was replaced by adipose tissue. CT with its clean demonstration pulmonary artery without any evidence of aquired obstruction of a pulmonary artery by pulmonary embolism or tumor invasion, maybe a valuable method for evaluaton of the unilateral absence of a pulmonary artery.