Four cases of multiple primary lung cancer were experienced at the department during the past twelve years. There were each two synchronous and metachronous cancers. Squamous cell carcinomas (SCC) were found in two cases, SCC and adenocarcinoma (AD) in one case, and adenosquamous carcinoma and AD in one case. Case 1. A 60-year-old man with SCC of the respiratory system underwent left lower lobectomy. There was a previous history of right middle and lower lobectomy seven years before. Case 2. A 67-year-old man with synchronous multiple lung cancer underwent right middle and lower lobectomy. Case 3. A 75-year-old woman had an adenocarcinoma of the left lingular segment 3 years after right middle and lower lobectomy for an adenosquamous carcinoma of the lung. As the patient refused any operation, radiotherapy was performed and she is alive bearing the cancer. Case 4. A 65-year-old man had SCCs in bilateral lower lobes due to chromium exposure. The patient underwent radiation and bronchial artery infusion, followed by left lower lobectomy. Then, laser therapy was scheduled for the lesion in the right lower lobe, however, the patient died of postoperative pneumonia. Some discussion on these cases of multiple primary cancer of the lung is presented, with a review of the literature.