The chemical interactions that occur between NO, SO2, and ClO2 are investigated. In focus is the oxidation of NO with gaseous ClO2 for simultaneous removal of NOx and SOx from combustion-derived flue gases. Laboratory-scale experiments were conducted to examine the conversion of NO to NO2, under the following conditions: temperature range of 100-180 degrees C; H2O concentrations in the range of 0%-25%; ClO2-NO molar ratios in the range of 0.2-0.6; and NO and SO2 flue gas concentrations in the ranges of 0-250 ppm and 0-1000 ppm, respectively. The results show that NO is oxidized efficiently by ClO2, whereas the ClO2-SO2 reactions are insignificant. The water concentration had no effect on oxidation, and the temperature had a limited effect, within the investigated ranges. The outcomes favor the process economics of the studied applications, since ClO2 consumption is negligible with respect to SO2 oxidation.