Patients with lung cancer are usually concerned about the risks of radiotherapy. In fact, radiation therapy plays a very important role in lung cancer, and more than 60% of all lung cancers will be treated by radiation therapy, whether early, locally advanced or late. The most common risks of radiation therapy for lung cancer are radiation pneumonia, radiation esophageal damage, radiation mucositis, then cardiovascular damage and systemic symptoms such as loss of appetite and fatigue. Therefore, lung cancer patients should not give up this important treatment because they are worried about the side effects of radiotherapy.