Supported copper-titanium oxide catalysts have been studied by IR spectroscopy, XRD, UV-VIS diffuse reflectance spectroscopy, ESR, TPR with hydrogen and EXAFS. Different states of Cu2+ ions have been found on the surface of TiO2. The ratio between these states depends on the copper concentration and catalyst preparation method. Chain structures are formed due to the interaction of Cu2+ ions with TiO2. Their concentration and geometry of their nearest oxygen environment are determined by the structure of anatase faces. Some of these surface-stabilized Cu2+ ions are nucleation centers of oxide clusters. A noticeable growth of bulk CuO phase is observed after the completion of the formation of chain structures and oxide clusters. A quantitative estimation of the concentration of these copper forms in the catalysts is reported. For supported copper-titanium oxide catalysts, chain forms of Cu2+ ions are shown to be the most active forms of copper in NO SCR with ammonia and methane oxidation.