The effect of Nb and Cr dopants as well as Sn4+ additions on the electronic structure of rf-sputtered TiO2 thin films and its subsequent influence on gas sensor performance is reported. The changes in the electrical conductivities of TiO2 thin films doped with up to 10 at.% Nb, 4 at.% Cr and TiO2-SnO2 in the full range of compositions upon exposure to hydrogen and oxygen are demonstrated. The spectral dependence of the absorption coefficient in the vicinity of the band gap transition of TiO2 is shown to be affected by doping.