An aortopulmonary septal defect or aortopulmonary window (APW) is a rare cardiovascular anomaly with direct communication between the ascending aorta and the main pulmonary artery leading to a left-to-right shunt. It is accompanied by other cardiovascular anomalies in approximately half of patients. In order to avoid irreversible sequelae, interventional or surgical treatment should be performed as soon as possible. Cardiovascular CT, as a fast, non-invasive technique with excellent spatial resolution, has an increasing role in the evaluation of patients with APW, enabling precise and detailed planning of surgical treatment of APW and associated anomalies if present. This article aims to review the anatomical and clinical features of aortopulmonary septal defect with special emphasis on its detection and characterization by a CT examination.