Activated carbons of different origins were studied as sulfur dioxide adsorbents. The materials were characterized using adsorption of nitrogen, titration, X-ray photoelectron spectroscopy, and thermal analysis. The investigation was focused on the role of nitrogen functionality and pore sizes in the process of SO2 adsorption/oxidation. The results showed that quaternary and pyridinic type nitrogen significantly enhance the adsorption capacity. It happens when catalytic centers are located in the small pores, which is likely to help in achieving high dispersion of these centers. Besides an oxidation effect due to the formation of active oxygen radicals, the nitrogen-containing centers attract the SO42-ions causing the gradual pore filling which is the most effective usage of the carbon pore space.