For ZnO doped with transition metals (TM) in addition to well known material properties new functionality and application in field of spintronics can be occurred. This application aspect especially has enhanced after theoretical prediction of room temperature ferromagnetism in ZnO doped with Mn [T. Dietl et al., Science, 287 (2000) 1019]. In our work TM (Fe, Co, Mn) doped ZnO thin films and nanocrystals are fabricated and their transport, magnetic, optical, magneto-optical properties are studied. The doped thin films were grown by pulsed laser deposition and ZnCoO nanocrystalline samples were prepared by chemical method. The most remarkable findings concerning to high-temperature ferromagnetic ordering was observed in case of Zn0.97Co0.03O thin films and nanocrystals. It was found that kind of magnetism is very sensitive to growth conditions, carrier concentration, impurity concentration and kind of available defects. In addition, probability of occurrence of the ferromagnetism is higher for oxide nanometric layers and nanoparticles than in case of bulk crystals. Obviously, this is suggestion of exhibition of surface effects. From point of view possible application the studied materials are considered as an active component in sensing and detecting devices, in which can combine usual semiconductor properties with both quantum confinement and spin-exchange interaction effects. In particular, it was studied multilayer structure consisting of ZnMnO and ZnO layers. This structure was used for analysis of spin injection and detection in external magnetic field by magneto-optical technique. The revealed features give new insight into controversial magnetic behavior of semimagnetic semiconductor oxides and their possible applications in transparent and spin electronics. The work was supported by grant from Ministry of Education and Science of Ukraine.