We reviewed clinical features of 6 primary lung cancer cases complicated with sarcoidosis admitted to our hospital from January 2006 to December 2010. The male/female ratio was 3/3, and the average age at the onset of the lung cancer was 63.8 years. Four cases had a history of smoking. A diagnosis of sarcoidosis and lung cancer was made at the same time in 4 cases, and in 2, lung cancer was detected during follow-up of sarcoidosis. The follow-up durations were 5.6 years and 22 years. In all patients, the diagnosis of sarcoidosis was made with a histological examination. A chest CT scan showed hilar lymphadenopathy in 4 cases; 2 were bilateral, and 2 were unilateral. In 5 cases, primary lung cancer was detected in the lower lobe and the sixth was in the upper lobe. Histological types of lung cancer were adenocarcinoma in 4 cases, bronchioalveolar carcinoma in 1, and small-cell carcinoma in 1. For evaluation of hilar lymphadenopathy, endobronchial ultrasound-guided transbronchial needle aspiration was performed in 1 case, and video-assisted thoracic surgery was carried out in another. We conclude that it is difficult to distinguish between lymphadenopathy of sarcoidosis and metastatic lesion of lung cancer by imaging methods. Thus cytological or histological examination of lymphadenopathy is important to decide on a treatment plan in a case of lung cancer with sarcoidosis.