We report 2 cases of pulmonary sarcomatoid carcinoma mimicking malignant mesothelioma. Case 1: A 69 year-old man presented, complaining of right chest pain. The chest X ray film and CT showed tumors in the right chest wall and pleura. Histological findings of specimens obtained from a percutaneous biopsy revealed spindle tumor cells, and the immunohistochemistry showed that the tumor cells were positive for CK-7, AE1/AE3, and vimentin and negative for calretinin, D2-40, and WT-1. We diagnosed pulmonary sarcomatoid carcinoma and started chemotherapy with carboplatin and paclitaxel, but it was ineffective. Case 2: A 68 year-old man was admitted complaining of general malaise. The chest X ray film and CT revealed tumors in the right chest wall. Histological findings showed necrosis and spindle tumor cells which were positive for AE1/AE3 and vimentin, and negative for calretinin, D2-40, and WT-1. We diagnosed pulmonary sarcomatoid carcinoma and started chemotherapy with carboplatin and paclitaxel. However the disease continued to progress and he died 2 months after admission. The pulmonary sarcomatoid carcinoma was reported to have spred to the pleural and chest wall. The present two cases showed prominent chest wall and pleural tumors with obscure primary lung tumors. Therefore, we needed to differentiate sarcomatoid carcinoma from malignant pleural mesothelioma.