Since HIV infection and opportunistic infections began to be treated by highly active antiretroviral therapy (HAART), the incidence of cancers, especially lung cancer increased. The clinical course of lung cancer in HIV infected patients is more aggressive, and little is known about its features or management. We retrospectively evaluated 6 cases of lung cancer with HIV infected patients in Tokyo Metropolitan Komagome Hospital. All patients were male and current smokers. Adenocarcinoma, squamous cell carcinoma and small cell carcinoma were observed in 3, 2 and 1, respectively. There were 2 cases each of clinical Stage I, IIIB, and IV were each 2 cases. The range of the CD4 cell count was 52-432/microL. HIV infection was confirmed concurrently with the diagnosis of lung cancer or complications in 5 of 6 patients. Some cases treated for both lung cancer and HIV, had a relatively good clinical course. We suggest that cancer treatment concurrently with HAART may be useful for similar cases. Further experience and study are necessary.