In nuclear medicine diagnostic procedures, specifically in PET/CT, in order to obtain information on metabolic changes within organs, radioactively labelled compounds composed of radioactive isotopes and carrier molecules called radiotracers are used, which enables the visualization of morphological and functional changes in organs and tissues. PET/CT is a modern diagnostic modality consisting of circular array of PET detectors and a classic CT scanner, which enables detection of annihilation produced photon pairs and their anatomical localization. Since radioactive isotopes, as parts of PET radiotracers, are positron emitters, their production requires the use of cyclotron, which can be limiting factor in their availability. With gradual progress throughout history, different methods of morphological imaging became insufficient for the diagnosis of certain diseases and that is why various radiotracers were discovered and developed, which are today used in many medical fields, primarily in oncology, neurology and cardiology. The most commonly used radiotracer for most indications is 18F-FDG, but a wide spectrum of other radiotracers, that show higher specificity for certain metabolic processes has been developed. In oncology, this enables precise detection and evaluation of malignant formations and metastases, staging, assessment of response to therapy etc. In addition, by indicating PET/CT in neurological patients, with the use of radiotracers, it is possible to detect and analyse many neurological changes caused by Alzheimer’s or Parkinson’s disease and epilepsy. Also, PET radiotracers have clinical significance in cardiology, when assessing the viability and perfusion of the cardiac muscle, but also in the detection of various inflammatory conditions.