Abstract: Objective: To investigate the effect of threedimensional conformal radiation therapy (3DCRT) on non-small cell lung cancer(NSCLC). Methods: We retrospectively analyzed 52 cases of IIV stage NSCLC treated with 3DCRTand 50 NSCLC cases treated with conventional radiotherapy. In the 3DCRT group, only tumor and lymph nodes withmetastasis were included in the clinical target, with 46 coplane or noncoplane shoot areas, at 23 Gy/fraction, onceper day, 5 times per week, with a total dose of 6672 Gy. In the conventional RT group, the shoot area contained obvioustumor and homonymy hilum of the lung, the mediastinum superior or holinterpleural space, and circa paraprick. Whenthe total dose reached 3640 Gy, we altered the oblique portally administered radiation in order to avoid affecting thespinal cord. The regimen was DT 1.82.0 Gy/fraction, once per day, 5 times per week, with a total dose of 6070 Gy. Results: The response rate (CR+PR) was 90.4% in the 3DCRT group and 72% in the conventional RT group, with a statisti-cally significant difference(P<0.01). The rate of improvement of clinical status was 96.5% in the 3DCRT group and 86.4%in the conventional RT group (P<0.01). In the 3DCRT group, the 0.5, 1and 2year overall survival rates were 92.3%,75.0% and 42.3%, respectively. In the conventional RT group, the 0.5, 1and 2 year overall survival rates were 76%,60% and 30%, respectively. A statistically significant difference was found in the 0.5year overall survival rate betweenthe two groups. No significant difference was found in the 1year and 2 year overall survival rates between the twogroups. The adverse reaction rates in the 3DCRT and the conventional RT group were 12.5% and 23.7%, respectively,with a statistically significant difference between the two (P<0.05). No cases with stageⅢ or higher in the 3DCRT groupexperienced severe adverse effects. Conclusion: 3DCRT is feasible for the treatment of NSCLC. 3DCRT has good thera-peutic effects with slight adverse effects, improves clinical symptoms, and is welltolerated.