Multiple primary lung cancers, either synchronous or metachronous, are unusual. We treated a 70-year-old man with double synchronous lung cancers in the right upper lobe, an adenocarcinoma and a squamous cell carcinoma. As multiple malignant lesions in an early stage may be curable, those patients in whom a lung cancer has already been detected, and who have an increased risk, such as long history of heavy smoking or of exposure to some carcinogens, an aggressive check-up should be performed and should be closely watched.