Magnetic and electrical properties of doped nanostructures can be tailored by varying the impurities concentration and distribution, cleverly manipulating their segregation degree. Currently used methods for mapping the nature and distribution of low concentration (< 1%) impurities are very complex and laborious. Moreover, the doping mechanisms at nanoscale are not yet completely elucidated. In this project we will use a comparingly simple, statistically relevant and nondestructive method for quantitative determination of the paramagnetic impurities distribution in ZnO nanostructures doped with transition metal ions (TMI), based on electron paramagnetic resonance (EPR) spectroscopy. We will identify by EPR the nature and concentration of impurities and intrinsic defects, the impurities quantitative distribution, as well as their evolution under annealing in ZnO nanoparticles and thin films doped with TMI in variable concentration up to 1%. The doped ZnO nanostructures will be characterized by X-ray diffraction and electron microscopy in transmission and scanning mode. These studies will significantly contribute to the understanding of the doping mechanisms at nanoscale, leading to applications in nanotechnology by optimizing the synthesis of nanostructures with desired impurities distribution, and in quality assurance of nanostructures of interest in spintronics, opto- and nanoelectronics.