A catalyst for treating exhaust gases having excellent durability and performance for removing nitrogen oxides and organic halogen compounds and a low SO2 oxidation rate, a titanium oxide suitable for preparing the catalyst and a method for treating exhaust gases containing nitrogen oxides and/or organic halogen compounds using the catalyst are provided.The BET specific surface areas of the titanium oxide and the catalyst for treating exhaust gases are in the range of 85 to 250 m2/g and in the range of 50 to 200 m2/g respectively. The titanium oxide and the catalyst for treating exhaust gases have each a ratio in the range of 15 to 145%, the ratio of the intensity of the peak indicating an anatase crystal present in the range of 2θ=24.7° to 2θ=25.7° of powder X-ray diffraction thereof (Ia) to the intensity of the peak indicating an anatase crystal present in the range of 2θ=24.7° to 2θ=25.7° of powder X-ray diffraction of the standard sample comprising a mixture composed of 15% by mass of pure anatase-type titanium dioxide and 85% by mass of pure rutile-type titanium dioxide (Ib).