Three patients with suspected persistent left superior vena cava (PLSVC) diagnosed by transthoracic echocardiography underwent single-plane transesophageal echocardiography. In all three patients transverse cuts through right atrium and coronary sinus demonstrated the presence of PLSVC. Agitated contrast injection into the left antecubital vein opacified PLSVC and coronary sinus in all cases. Transesophageal echocardiography is superior to transthoracic echo in the diagnosis of PLSVC and associated cardiac anomalies.