We present images from a cardiovascular magnetic resonance (CMR) study that enabled the rapid, non-invasive, complete diagnosis of a previously unreported congenital anomaly. Cor triatriatum of the left atrium thought to be an anomaly of the embryonic pulmonary venous connection to the left atrium. In association with this, many types of partially anomalous pulmonary venous connection are described, but we know of no previous description of pulmonary venous egress occurring on the right side, via the azygos vein.