An anomalous course of the left brachiocephalic vein behind the aortic arch was identified in a patient with tetralogy of Fallot. A 6-year-old male patient had been admitted to the hospital with a diagnosis of tetralogy of Fallot and patent foramen ovale. At the beginning of the operation the left brachiocephalic vein could not be found. The pericardium was opened longitudinally and there was no persistent left superior vena cava. After careful examination, the left brachiocephalic vein was found behind the aorta. Especially during open heart surgery this pathology is very important. We conclude that when the left brachiocephalic vein can not be found, the possibility of persistent left superior vena cava and retro-aortic left brachiocephalic vein should be borne in mind.