The effect of NO2 on the desulfurization reaction of simulated flue gas by Ca(OH)(2) was investigated in a fixed-bed reactor at 333-353 K and at relative humidities (RHs) in the range of 30%-70%. NO2 was determined to be a promoter for SO2 uptake, because its retention can be increased up to 200%. The effect of NO2 and O-2 concentration on the kinetics of the desulfurization reaction was surveyed and successfully simulated by means of a deactivation model implemented with an inverse shrinking-core model (DM-ISCM). Solid analyses were also performed to identify the reaction products and provide insight into the chemistry of the process.