We report the case of a 2.5-year-old boy with atrial septal defect in whom anomalous position of the left innominate vein was detected on preoperative ultrasound examination. Before joining the right brachiocephalic vein, the vessel extended from the left to the right and downward beyond the descending aorta. It was considerably flattened by the thoracic vertebral column, and was invisible on ultrasonography in this section. The appearance of the visible segments raised a suspicion of an anomalous course of persistent left superior vena cava draining into the left atrium, dilated azygos vein in a case of interrupted inferior vena cava, or partial anomalous pulmonary venous return. Since all doubts had to be resolved before open heart surgery, a decision was made to expand the diagnostic work-up to include computed tomography angiography. We present the echocardiographic and computed tomography findings of this unusual and previously unreported case of anomalous venous return.