Two patients with congenital atresia of the left coronary artery ostium underwent myocardial revascularization at the age of three years and three months, respectively. The patients were admitted to the hospital with a clinical history of sudden chest pain or short apnea not necessitating resuscitation. Non-invasive examinations and hemodynamic studies revealed dysfunction of the left ventricle and ostial atresia of the left coronary artery. Surgical revascularization-bypass grafts were performed using the left internal mammary artery and saphenous vein graft in the first case and the left internal mammary artery in the second child. Both patients survived surgery and good patency of the grafts was confirmed by coronary angiograms during hospital stay. These cases are interesting because of their rarity and diagnostic and therapeutic difficulties.