The incidence of synchronous multiple primary malignancies has been reported to be low. We report a rare case of synchronous lung squamous cell cancer and small cell lung cancer in an 82-year-old male patient. There is a lack of standard diagnostic criteria for multiple primary lung cancer. Two tumors with similar morphology are difficult to draw conclusions about the same lineage or different lineages. If the patient's physical condition permits, multiple tumors should be sampled and tested. Besides, imaging features are helpful for identification. It is advisable to diagnose synchronous multiple primary malignancies in an early stage, which contributes to a favorable outcome.