Radiotherapy is an important component of non-small cell lung cancer (NSCLC) treatment for both curative and palliative purposes. Regarding the curative intent, radiotherapy of inoperable tumours can be performed preoperatively, postoperatively, or definitively. For patients with early-stage NSCLC that is unsuitable for resection, local high-dose radiotherapy is the treatment of choice. Stereotactic radiotherapy has been demonstrated to be an effective treatment approach for early-stage tumours, combining the accurate focal dose delivery of stereotactic techniques with the biological advantages of dose-escalated hypofractionated radiotherapy, achieving local control rates of up to 90% and favorable results, especially for patients with a good performance status. Postoperative radiotherapy should not be used for stage I or II NSCLC, and its use remains controversial for resected stage IIIA (N2) disease. To increase the efficacy of radiotherapy, chemotherapy can be used concurrently, resulting in better results as well as increased toxicity. Concurrent chemoradiotherapy is presently the standard treatment for stage III inoperable NSCLC. Within this treatment framework, conventional fractionated radiotherapy at a total dose of 60–66 Gy has proven effective. The chemotherapy should be performed using a cisplatin-based regimen or, if contraindicated, a carboplatin-based regimen. For metastatic disease, short-course palliative treatment with hypofractionated schemas is preferred, and prolonged palliation effects (6–12 months) can be achieved in many cases. There is a close relationship between dose escalation and efficacy; that is, a better outcome is achieved with higher doses. New drug combinations with better radiotherapy techniques will result in better local control and overall survival without increasing toxicity.