Structural effects on the oxygen reduction reaction (ORR) have been studied on the low index planes of rutile TiO₂ doped with Nb (0.05–1 wt%) in 0.1 mol L⁻¹ HClO₄. The order of the ORR activity at 0.20 V (vs. RHE) is TiO₂(100) < TiO₂(111) < TiO₂(110), and the activity increases with increasing Nb concentration. The activity of TiO₂(110) is 5.6 times as high as that of TiO₂(100) at Nb concentration 1 wt%. The order of the ORR activity does not correlate with the amount of oxygen vacancy defects that are known as the active sites of the ORR of TiO₂ nanoparticles. The ORR activity of 1 wt%Nb-doped TiO₂(100) modified with melamine is 2.1 times higher than that of the unmodified one. The activity of 1 wt%Nb-doped TiO₂(110) modified with melamine is the highest in the low index planes of TiO₂. Modification by tetra–n–hexylammonium cation (THA⁺) affects the ORR activity slightly.