Radiotherapy is a therapeutic method of local treatment of tumors and other types of diseases using highenergy ionizing radiation. Teleradiotherapy is a type of radiation in which the radioactive source is located inside the teleradiotherapy device. The devices used in teleradiotherapy are a linear accelerator and an almost abandoned cobalt unit. Accelerators are devices that, using electric and magnetic fields, accelerate charged particles to high speeds, sometimes even to speeds that are slightly less than the speed of light. Diagnosis and treatment of cancer are complex processes that require the knowledge and expertise of oncologists first, and then other members of the oncology team. The accelerated development of technology is proportional to the development of linear accelerators. Experts continuously work on improving them with the aim of using ionizing radiation as precisely and efficiently as possible for therapeutic purposes. Radiotherapy is a treatment method that implies precision in the deepest sense of the word. Precision must be present with the oncology team when creating the radiation plan, the medical radiology engineer when handling the linear accelerator and positioning the patient, as well as with the device itself. Accordingly, it is necessary to constantly carry out quality control of the linear accelerators themselves. Constant education of the oncology team, i.e. experts who perform radiotherapy using a linear accelerator, is extremely important in order to ensure the best possible care.