Among coronary vessels anomalies is the rare coronary artery fistula. Myocardial insufficiency resulting from fistula steal phenomenon can not be clinically distinguished from that of coronary atherosclerosis, if these conditions coexists in the same patient. The authors present a case of extracardiac left coronary artery fistula connecting the circumflex branch and left bronchial artery, with inferior wall myocardial insufficiency attributable to the right coronary artery atherosclerosis.