Surface area and composition of nominally pure, Al- and Si-doped TiO2 (anatase) nanoparticles were investigated. There is a clear evidence for Si segregation in pure and Si-doped TiO2; the data for Al-doped samples can be interpreted by cosegregation of Al and Si. The electrical conductivity of CuBr-TiO2 (20 vol%) composites using pure, Al- and Si-doped TiO2 was investigated by impedance spectroscopy. The observed conductivity modifications can be related to the phase boundary chemistry, especially to the interactions between Cu+ ions and OH surface groups of TiO2.