Surgery alone can cure 40-85% of patients with localized non-small cell lung cancer, depending on tumor stage and metastatic lymph-node involvement. As local failure rates occur in up to 50% of the cases, postoperative radiotherapy as an adjuvant treatment option has been evaluated in several trials. This review briefly summarizes the published data mainly from randomized trials. While most of the studies showed a decrease in local recurrence rate, especially in stage-III/N2 tumors after postoperative radiotherapy, no impact could be shown on overall survival. In early stages a detrimental effect of postoperative radiotherapy has been postulated, but those findings have to be interpreted with caution as radiation techniques used were suboptimal and probably not today's state of the art. A carefully designed randomized trial using modern radiotherapy techniques is warranted to define the impact of irradiation on completely resected NSCLC.