The three main treatments for tumors are radiotherapy, chemotherapy and surgery, etc. Many people are confused about the difference between radiotherapy and chemotherapy. Many people are confused about the difference between radiotherapy and chemotherapy and often confuse these two treatments. In fact, there is a big difference between radiotherapy and chemotherapy. First of all, the treatment methods are different: radiotherapy is radiation therapy, which is a treatment method of using various kinds of energy rays to irradiate tumors in order to inhibit and kill cancer cells, commonly known as “baking electricity”. Chemotherapy, on the other hand, is the application of chemical drugs (including endocrine drugs) to treat malignant tumors. Chemotherapy drugs are often injected intravenously, taken orally or in other forms to kill tumors in the body. Secondly, the scope of treatment is different: radiotherapy, like surgery, is mainly local treatment, and the scope of radiotherapy is called “target area”, i.e., the area where the radiation is concentrated. After determining the size of the tumor and its invasion site based on imaging and other clinical examinations, radiotherapists must also understand the biological characteristics of the tumor and the law of spread before deciding the radiation scope. Chemotherapy is a systemic treatment, and the drug will be distributed to all parts of the body after entering the body, which has a strong effect not only on solid tumors, but also on small invisible metastases. Of course, there are also local treatment-based chemotherapy such as interventional chemotherapy, local infusion chemotherapy and so on. Thirdly, the indications are different. Radiotherapy is mainly used for the radical treatment of relatively limited solid tumors, such as head and neck tumors, lung cancer, esophageal cancer, skin cancer, lymphoma, etc.; adjuvant treatment of some tumors such as breast cancer, cervical cancer, gastrointestinal tumors and adjuvant treatment; some other tumors such as bone and brain metastases are treated with palliative radiotherapy, etc., while for systemic tumors such as leukemia, the effect is limited. At present, about 70% of tumor patients need to receive radiotherapy at different stages of the disease process, which shows the importance of radiotherapy in tumor treatment. Chemotherapy is used for tumors that are sensitive to chemotherapy drugs, such as lymphoma, leukemia and other hematologic diseases, breast cancer, gastrointestinal tumors, lung cancer, reproductive tumors and so on. The effect of chemotherapy depends on the type and condition of the tumor, some of which can be cured and more often inhibit the growth and spread of the tumor. With the emergence of new technologies, the indications for radiotherapy are changing. Fourthly, the toxic side effects are different. Generally speaking, radiotherapy is mainly local reactions, which are related to the radiotherapy field. For example, head and neck radiotherapy may cause dry mouth, sore throat, neck fibrosis, loss of taste function and so on. Radiotherapy to the chest may result in radioactive lung changes, radioactive esophagitis, etc. With the advancement of radiotherapy technology, radioactive brain damage and paraplegia, which used to occur frequently, are less common. The main reactions to chemotherapy are systemic reactions, usually bone marrow suppression, gastrointestinal reactions, such as decreased blood count, nausea, vomiting, and phlebitis. With proper management, serious liver and kidney damage, cardiac damage, and severe reactions such as “vomiting out the bile” are not very common in clinical practice. Nowadays, technology is developing, and the toxic side effects of radiotherapy are gradually being reduced. Although radiotherapy and chemotherapy are so different, in fact, radiotherapy, chemotherapy and surgery are used in conjunction with each other in the treatment of many tumors. Breast cancer and lung cancer are the most common cases of comprehensive treatment. As for the treatment of tumor, the decision of when to operate, when to radiotherapy, when to chemotherapy, and when to palliative care depends on the clinicians, imaging physicians, pathologists, and related medical personnel through a comprehensive judgment of the patient’s disease stage, physical condition, and other general conditions.