To the authors' knowledge, no study regarding lung carcinoma patients age <30 years has been published. Therefore, this study was undertaken to define the characteristics of lung carcinoma patients age <30 years. Information regarding 26 patients with primary lung carcinoma who were age <30 years was obtained from 10 medical institutions and reviewed retrospectively. For comparison, 304 patients age > or = 30 years who were admitted to the First Department of Internal Medicine at Toyama Medical and Pharmaceutical University between 1980-1996 were studied. Among the characteristics observed in the group of lung carcinoma patients age <30 years was a high incidence of female gender, no history of smoking, so-called "low grade malignancy," American Joint Committee on Cancer Stage I disease, and previous surgical resection. In addition, a low incidence of squamous cell carcinoma was noted, and a more favorable prognosis was observed. The current study noted clinical features that could be defined clearly in lung carcinoma patients age <30 years.