Applications of radiation in medicine is based on the radiation ability of destroing the tumor cells and creating the images of internal organs. This two features play an important role in the diagnosis and treatment of diseases by radiation. In medicine X-ray and radionuclides being sources of gamma rays as Tc-99m, I-137, or Tl-201 are used for the diagnosis of diseases, as beta particles uses for the treatment of diseases. In nuclear medicine radioactive isotopes are built into pharmaceuticals and create radiopharmaceuticals. Radiopharmaceutical administered to patient gathers in examined organ and gives information on functional and anatomical status of the organ. Radiation workers prepare radiopharmaceuticals, transport it, implement, take diagnostic images and survey the therapy. Their radiological protection is very important. Efficient radiation protection can be achieved by factors of time (reduce the time spent close to radioactive source to minimum), distance (keep maximal distance to radioactive source), and shielding (sufficient amount of protective material placed between the source and body) concepts are the basis.