Background: Surgical resection is the treatment of choice for localized, operable non-small cell carcinoma of the lung. Curative radiotherapy, however, is considered an alternative to surgery in patients with poor performance state, poor cardiopulmonary function, or who refuse surgery. However, the difference in prognosis after surgery and radiotherapy is not well established in the patients with stage I non-small cell lung cancer. Method: To evaluate the difference in progonsis between surgery and radiotherapy in stage I non-small cell lung cancer, a retrospective study was done with 15 patients treated with curative radiotherapy and 24 patients treated with curative surgery. Results: The overall response rate was 80%, with 33% complete response, after radiotherapy. The median survival time of the patients with radiotherapy was 14.9 months, with 2-year and 5-year survival rates of 22% and 0%, respectively. The median survival time of the patients with surgery was 37.7months, with 2-year and 5-year survival rates of 65% and 41%, respectively. Conclusion: These results suggest that surgery is better than the radiotherpy in view of survival rate and it is necessary to recommend, more strongly, curative surgery to patients with stage I non-small cell lung cancer if the patients are able to receive operation. To compare, more accurately, the difference in prognosis by the modality of therapy, large multicenter study is needed.