A 66-year-old man was admitted to our hospital for detailed investigation of an abnormal shadow on his chest X-ray. Chest radiography and computed tomography(CT) of the chest showed mediastinal lymphadenopathy and a tumor shadow in the left upper lobe. Biopsy of the mediastinal lymph nodes by mediastinoscopy showed that sarcoid nodules existed in all the biopsies nodes. Therefore, the lymphadenopathy was thought to be sarcoidosis or sarcoid reaction accompanied with lung cancer. Left upper lobectomy and dissection of hilar and mediastinal lymph nodes were performed. Although sarcoid nodules were seen in all the dissected lymph nodes, the cancer involved #5 and #14 lymph nodes. He died of brain metastasis 10 months after surgery.