Twenty-three primary lung cancers have been proven. Of these, 20 presented as nodules: 19 were detected during the initial screening, and 1 was detected on an incidence screening. The stage distribution was available for 17 of these 20 subjects (stage I, 9 subjects; stage IIA, 1 subject; stage IIB, 4 subjects; stage IIIA, 2 subjects; stage IV, 1 patient). The cell types were adenocarcinoma (eight subjects), squamous cell carcinoma (six subjects), small cell carcinoma (one subject), and neuroendocrine tumor (one subject). Of the 20 lung cancers presenting as nodules, 16 (80%) were detected on the initial LD or FD CT scan. The size distributions of nodules seen on HD CT scans were 9.4 to 19 mm (eight subjects), 20 to 29 mm (eight subjects), and ≥ 30 mm (four subjects). Three of the 20 subjects were nonsmokers. We have observed many cases of multiple nodules (ie, more than six nodules) and many nodules of > 1 cm that have not increased in size. None of the indeterminate nodules seen at 6 months that has reached the 12-month follow-up (65%) has grown.