Cor triatriatum, although rare in adults, is often associated with anomalous pulmonary venous return. Accurate diagnosis of the pulmonary venous return and its anatomic connections is essential in planning proper surgical correction. This case illustrates the advantage of selective pulmonary artery angiography in obtaining accurate detail of the pulmonary venous anatomy from digital subtraction levophase images. Selective right and left pulmonary angiography was performed using a balloon catheter to simultaneously occlude the opposite pulmonary artery. This technique was well tolerated and greatly enhanced visualization of the anomalous pulmonary venous connections, allowing proper planning for corrective surgery.