The incidence of synchronous colorectal and lung cancer is relatively rare. We report three cases of patients with tumors located in the rectum, ascending colon, the lower lobe of the left lung, and the upper lobe of the right lung. Synchronous curative resection of the two lesions was performed in two patients, whereas colectomy was performed in an elderly patient with a poor lung function. Pathological examination showed the colorectal cancer was a moderately differentiated adenocarcinoma and the lung cancer was a squamous cell carcinoma. Surgical treatment and postoperative adjuvant chemotherapy for the lung cancer were different from those for colorectal cancer with pulmonary metastasis. If possible, radical resection should be performed for each cancer when synchronicity is found. The incidence of synchronous colorectal and lung cancer is relatively rare. We report three cases of patients with tumors located in the rectum, ascending colon, the lower lobe of the left lung, and the upper lobe of the right lung. Synchronous curative resection of the two lesions was performed in two patients, an colectomy was performed in an elderly patient with a poor lung function. the lung cancer were different from those for colorectal cancer with pulmonary metastasis. If possible, radical resection should be performed for each cancer when synchronicity is found.