The presence of only a single coronary artery is a rare congenital coronary artery anomaly. In most cases, it is an incidental finding on coronary angiography and has no clinical significance. However, it can cause angina, myocardial infarction or even sudden death, particularly in young patients in whom the course of the artery runs between the aorta and pulmonary artery. In such cases, angiographic assessment may be difficult. Multislice coronary computed tomography might be better for visualizing the anatomy of the coronary artery tree in these patients. This article describes the cases of three patients with a single coronary artery and associated atherosclerotic coronary artery disease in whom a diagnosis was made using coronary angiography and multislice computed tomography.