Differences in the histological manifestation of synchronous lung cancers are rare. Synchronous multiple primary lung cancers (SMPLC) are associated with long-term tobacco use, which could independently lead to mutations in the p53 and K-ras genes. We present the case of an 82-year-old man who smoked 30 cigarettes daily for the past 60 years. CT of the chest showed a right upper lobe mass. Bronchoscopy revealed an intra-lumen nodular lesion in the right lower lobe bronchus. The diagnoses of small cell lung carcinoma (SCLC) of the right upper lobe and non-small cell lung carcinoma (NSCLC) of the right lower lobe were confirmed by the morphologic features and the detected immunoreactivity. Immunohistochemical analyses showed a strong positive reaction for p53 in samples of the SCLC and NSCLC. The cancers had a different phenotype, but similar genetic abnormalities may have developed due to the carcinogens in the cigarettes.