Radiation therapy is a method of treating malignant head and neck tumors. Although it shows excellent treatment results, it is connected with numerous side effects in the oral cavity which significantly deteriorate the quality of life of a patient. Its effect is based on ionizing radiation which causes cell death. Apart from having an effect on tumor cells, it also affects healthy cells, especially those that are rapidly dividing. Therefore, frequent oral complications in the oral cavity are common. Dentists have an especially important roe in the treatment of patients before, during and after radiation. The goal of dental evaluation pior to radiation therapy is to eliminate pathological conditions and approach radiation therapy with a completely healthy oral cavity. Today, there are numerous protocols of dental assessment prior to radiation whose goal is to reduce and prevent oral complications. During the first valuation, dentists have to establish good communication with a patient and stress the importance of regular visits. Patients are given advice on maintaining good oral hygiene and are educated on possible side effects and a way of preventing them. When radiation therapy ends, patients must continue maintaining good oral hygiene and have regular visits with their dentist. In conclusion, the role of a dentist is to completely heal the oral cavity prior to radiation, to continue to monitor the patient during radiation therapy and after it ends. All this is done in order to improve and preserve oral and general health and to improve the quality of life.