TiO2 is known as a low-temperature selective catalyst for the reduction (LT-SCR) of NO with NH3. Furthermore, it is well-known that the oxidation of NO over the catalyst plays an important role in the LT-SCR. Adsorption of SO2 and NO over two kinds of TiO2 catalysts was investigated using a conventional flow type fixed-bed reactor at 100 degrees C under atmospheric pressure. The effect of the presence of SO2 on the adsorption of NO over the catalysts and the formation NO2 from NO was studied. The relationship between the NO2 formation, the NO adsorption, and the SO2 adsorption was also studied. The presence of SO2 was essential for the oxidative adsorption of NO over the catalysts. SO2 was adsorbed and converted to SO42-, then NO adsorbed on the SO2 pre-adsorbed catalyst and converted to NO3-. The presence of both SO2 and NO contributed to the formation NO2 from NO over the TiO2 samples. It was found that NO2 was evolved from an equimolar reaction of NO and SO2.