In order to clarify the role Of SO2 in the removal of mercury from coal combustion flue gas by activated carbon, the removal of Hg-0 vapor from simulated coal combustion flue gas containing SO2 by a commercial activated carbon (AC) was studied. ne Hgo removal experiments were carried out in a conventional flow type packed bed reactor system with simulated flue gases having a composition of Hg-0 (4.9 ppb), SO2 (0 or 500 ppm), CO2 (10%), H2O (0 or 15%), O-2 (0 or 5%), and N-2 (balance gas) at a space velocity (SV) of 6.0 X 10(4) h(-1) in a temperature rang 60- 100 degrees C. It was found that, for SO2 containing flue gas, the presence of both O-2 and H2O was necessary for the removal of Hgo and the Hgo removal was favored by lowering the reaction temperature in the order of 60 > 80 > 100 degrees C. The presence of SO2 in the flue was essential for the removal of HgO by untreated activated carbon. The activated carbons pretreated with SO2 or H2SO4 Prior to the HgO removal also showed Hgo removal activities even in the absence of SO2; however, the presence of SO2 also suppressed the Hgo removal of the SO2-pretreated AC or H2SO4 preadded AC.