We describe two cases of anomalous origin of the left lower-lobe pulmonary artery from the right pulmonary artery. The primary diagnosis was mitral atresia, hypoplastic left ventricle, aortic arch hypoplasia in the first child, and tetralogy of Fallot in the second. In both cases, the pulmonary trunk gave rise to a left pulmonary artery in the normal position. In addition, a second branch of the left pulmonary artery arose from the right pulmonary artery, and passed posterior and inferior to the left main or upper-lobe bronchus to supply the left lower lobe. In this review, we compare our findings with previously reported examples of this extremely rare cardiac malformation, and discuss possible embryological explanations for the lesion.