Twenty-six cases with lung cancer diagnosed by open-lung (n = 11) or thoracoscopic (n = 15) biopsy were analyzed. Mean tumor size was 19 mm. Biopsies were conducted due to the appearance of a nodular shadow determined by the retrospective X-p films in 13 cases, nodular shadow enlargement in 9, the positive suspicion of malignancy X-p findings without retrospective films in 3, and nodular shadow enlargement after medication of anti-tuberculosis drugs in one. Histology was adenocarcinoma in 18 cases, squamous cell carcinoma in 4, large cell carcinoma in 3, and adenosquamous cell carcinoma in one. The tumor stage was T1N0M0 in 14 cases, T1N0M0 in 3, T1N2M0 in 3, and unknown N factor because of lung wedge resection in 6 cases. Motality due to tumor recurrence was T1N2M0 in 3 cases and T1N1M0 in one. The remaining 22 cases survived without tumor recurrence. In short, small pulmonary nodules newly appearing or becoming with enlarged or found by retrospective X-p films should be conducted positively in thoracoscopic biopsy because of the high possibility of malignancy. Even if the tumor is small, lobectomy with lymph node dissection should be done, because of the very likely lymph node metastasis.