Nanocrystalline TiO2 powders with average crystallite sizes of 9-15 nm were synthesized by the solvothermal method and employed as supports for Co catalysts. The value of H-2 chemisorption/specific surface area of Co/TiO2 increased significantly with increasing TiO2 crystallite size. It was suggested that the higher amount of Ti3+ surface defects on the larger crystalline TiO2 resulted in a stronger interaction between Co and TiO2, hence, higher dispersion of Co was obtained.