After the discovery of X-rays a hundred years ago, it was found that X-rays can cause personal injury. Ionizing radiation is a form of radiation that has sufficient energy that causes ionisation of atoms and / or molecules. At sufficiently high doses of ionizing, radiation can damage important molecules in the cell, such as DNA, which can lead to adverse health effects. When working with ionizing radiation, because of the many adverse impacts, there must be implemented protection of the patient, the staff and the environment. First of all, the application of ionizing radiation must be justified, and during the application we must respect the limits of radiation dose to patients. The purpose is to keep the adverse effects of radiation minimized, which we can achieve by having a good understanding of physical properties of radiation, it's biological effects and by using all possibilities of prevention and protection against ionizing radiation. The radiologic technologist should participate in many aspects of patient care and prevention of ionizing radiation. He should apply appropriate measures and procedures, use the proper equipment and supplies, perform services with accepted standards and demonstrate expertise. All this with the aim to ensure that patients and staff are exposed to minimal radiation dose in accordance with the optimal diagnostic quality of patient. There are several forms of ionizing radiation, such as legislative protection, physical and technical protection, chemical protection, biological protection and scientific research. The application of all forms of protection makes radiation exposure of the patient population minimized with desirable medical effect. Legislative protection is very important because its strict regulations and laws are governing all forms of ionizing radiation. All regulations and laws governing legislative protection radiation exposure of staff and patients are available for everyone to read publicly. Physico-Technical protection fulfills the conditions that ensure the safety and security of premises, equipment and sources of radiation, the plant in which are located the sources of ionizing radiation or performing procedures involving ionizing radiation, protective equipment and personal protective equipment resources. The physical and technical protection is the most important part in the use of funds to ensure the protection of the X-ray devices and also personal protective means to protect professional staff and patients. There are other options for protection against ionizing radiation, of which the most important are: increasing distance from the source of ionizing radiation (radiation decreases with the square of the distance, ie doubling of distance from the source reduces the intensity of the radiation four times), shortening the duration of irradiation and mode (narrowing of the X-ray beam air, use and storage of personal protective equipment, the direction of the primary beam, etc.). Quality assurance and control are one of the essential facts to protect the patient from ionizing radiation, which indirectly affects the radiation dose reduction which is sometimes our choice of protection. Particular attention should be paid to the protection of young women and men, and especially children. Because of the role of women in creating offspring, it is very important to pay attention on their prevention and protection, as well as knowledge of effects of radiation and the risk of fetal damage in different stages of pregnancy. The radiologic technologist must also perform additional specific training in radiation protection in certain radiological procedures such as the protection of patients and staff at enlightening protection when shooting teeth protection in operating rooms, interventional radiology, etc. Protecting patients in the radiotherapy varies greatly and is more complex than protection in diagnostic radiology. Protection of patients in radiotherapy is related to quality assurance and control of radiotherapy devices and precise determination of the target volume. Protection of a patient exposed to radiation in nuclear medicine is achieved by selecting the appropriate radionuclides (energy and half-life), and selecting appropriate methods of acquisition and image processing. Radiation is an essential fact of human life and it has definitely been used to improve human life despite all the adverse effects that it causes. Although, it is sometimes difficult to assess whether a patient will have more benefits or harm of the examination, if ionizing radiation is used efficiently, it's benefit to the patient will be greater than the harmful effects of radiation. This is achieved by applying the ALARA principle (as low as reasonably archievable) which is using the lowest possible dose that can be achieved for optimal diagnostic information.