We experienced with two cases of left superior segmental resection for lung cancer with the left A4 + 5 which arose from pars mediastinalis. Left superior segmental resection was performed on a 67-year-old female and an 81-year-old male. In both cases we divided A4 + 5 temporarily and anastomosed to pars interlobaris of the left pulmonary artery. As a result, it was able to perform safe division of bronchus. In cases with A4 + 5 arising from pars mediastinalis, operation is difficult and risky because A4 + 5 locates in front of the left upper lobe bronchus. It is safer to reconstruct A4 + 5 on pars interlobaris of the left pulmonary artery in such cases.