We report the successful treatment of a 48-year-old man with left lung cancer and contralateral partial anomalous pulmonary venous return (PAPVR). He was found to have an abnormal shadow on a regular checkup. Sputum cytology revealed squamous cell carcinoma. Chest computed tomography showed not only a left hilar mass but also showed that his right superior pulmonary vein was draining into the high portion of the superior vena cava. In the presence of the right partial anomalous pulmonary venous return, it was believed that left pneumonectomy would cause serious postoperative heart failure due to an increase in the left-to-right shunt. Therefore his partial anomalous pulmonary venous return was corrected first under cardiopulmonary bypass, and 3 weeks later he underwent successful radical left pneumonectomy.