BACKGROUND Several investigators have reported on the risk of limited resection in patients with small peripheral lung cancer. Primary peripheral lung carcinomas 1 cm or less in maximum dimension were reviewed to study the feasibility of limited surgery. METHODS Among 1,051 lung cancer patients who underwent surgical resection of the lung in the National Cancer Center Hospital East, Kashiwa, Chiba, Japan, from January 1986 through March 1997, there were 13 patients who had untreated peripheral cN0M0 tumors 1 cm or less in maximum dimension on the resected specimens who underwent systematic mediastinal dissection. Their specimens were histopathologically reviewed. RESULTS There were ten adenocarcinomas, one small cell carcinoma, one poorly differentiated squamous cell carcinoma, and one typical carcinoid tumor. One adenocarcinoma showed lymphatic vessel invasion, venous invasion, and a subcarinal node metastasis. The small cell carcinoma was accompanied by a lymph node metastasis in a segmental node. The small cell carcinoma and another adenocarcinoma showed lymphatic vessel invasion. Of the ten adenocarcinomas, six were Noguchi's type B and four were type C. CONCLUSIONS Even among the pulmonary peripheral cancers smaller than 1 cm in diameter, more than one third showed an invasive nature. This fact must be considered in selecting limited resection in these patients. It is evident that tumor size alone cannot be an indicator for limited resection in lung cancer patients.