Lung cancer remains the number one cancer killer for both men and women in the United States. Most patients with lung cancer will receive radiotherapy as part of their treatment. For non-small cell lung cancer, this treatment will be administered as either neoadjuvant, adjuvant, definitive, or palliative therapy. Occasionally the distinction between these classifications may be unclear or may change in the course of the treatment. The use of thoracic radiotherapy as part of the treatment regimen and the goal of the therapy depends not just on tumor-related factors such as stage, but also on patient-related factors such as pulmonary reserve and performance status. This article describes the use of radiotherapy in each of the previously listed capacities and details the potential benefits and complication of this treatment modality for non-small cell lung cancer.