The incidence of lung cancer has been increasing among HIV-positive patients. The majority of these cases were in patients previously diagnosed as HIV-positive and treated with highly active antiretroviral therapy (HAART). Here, we report a 56-year-old male patient with lung cancer, who was diagnosed as HIV-positive after the onset of neck pain and lumbago and thus, was not treated with anti-AIDS therapy. The patient developed rapidly progressive and fatal respiratory failure. Autopsy demonstrated giant cell carcinoma of the lung responsible for carcinomatous lymphangitis. This case highlighted the possibility that pulmonary carcinogenesis in HIV-positive patients is not necessarily associated with HAART therapy.