Anomalous coronary arteries cause only uncharacteristic symptoms and are therefore often an incidental finding during conventional coronary angiography, with an incidence of 0.3-0.8%. The commonest anomaly is an aberrant origin of the main left or right coronary artery from the wrong sinus of Valsalva. Rarely there is a fistula draining into one of the cardiac cavities (right ventricle, right atrium, left ventricle or, rarely, superior vena cava) or displaced connection, as seen in anomalous origin of coronary artery from the pulmonary artery, resulting in a left-to-right shunt. In congenital heart disease, especially Fallot's tetralogy, the incidence of abnormal coronary arteries may be 2% or more. The proximal course in the former category may be misdiagnosed in up to 50% of cases. Aortic root injection with subtraction angiography, further detailed investigation with transoesophageal echocardiography or magnetic resonance angiography are therefore required as these have potential implications on subsequent surgery. Because of the abnormal course between aorta and pulmonary artery/outflow tract of the right ventricle and acute angulation there is a risk of angina, acute myocardial infarction or sudden death during or after exercise. It is therefore important to identify the exact cardiac anatomy, particularly in patients undergoing angioplasty, stenting or cardiac surgery.