Abstract: TiO2 oxide nanoparticles co-doped with Sb/Dy ions were synthesized by a hydrothermal precipitation method. Some amount of the synthesized co-doped sample was hydrogenated at *550C for 30 min. The samples were characterized by traditional methods: structural investigation by X-rays, an optical investigation by spectral diffuse reflectance and AC dielectric measurements. It was noticed that 3%-Sb/Dy co-doping induces growth of mixed (Anatase ? rutile) TiO2 phases. The different styles of doping of Sb5? and Dy3? ions into TiO2 nanocrystallites can be utilized to produce core/shell construction for the creation of colossal permittivity (CP). Thus, the dielectric permittivity for Sb/Dy co-doped TiO2 was found to be of order *103 at 1 kHz. The hydrogenation was found to reduce the CP by influencing the core/shell constructions as well as by the creation of a high density of itinerant electrons, which could be estimated by the optical measurements. This result is important from point of view of studying the influence of hydrogenation on the dielectric properties of nano-sized transparent conducting oxides. The created CP was explained, in the present work, within the framework of the core/shell model and doping mechanisms. Such important results will be useful for future work on using hydrogenation to support/reduce CP depending on the types of dopant ions.