Mixtures of Ca(OH)2 and different siliceous materials such as fly ash, bentonite, silica fume, and diatomite were hydrated to produce reactive SO2 sorbents. It was observed that these sorbents showed a better reactivity toward SO2 than the Ca(OH)2 itself. This behavior is closely related to the pozzolanic nature of the hydrated sorbents and to the greater surface area. The reactivity of the sorbents was strongly influenced by the source of siliceous material and the hydration conditions. The total sulphation capacities of the sorbents were determined at 338 K with a synthetic gaseous mixture containing 5,000 ppm SO2 and 55% relative humidity. Depending on the chemical and physical properties of the sorbents, the SO2 captures ranged from 1.20 to 5.58 mmol SO2/g sorbent. The amount of SO2 capture increased with the increasing surface area of the sorbent. The utilization of Ca(OH)2 with SO2 improved significantly when Ca(OH)2 was hydrated with siliceous materials first and later exposed to SO2. Copyright © 1999 Taylor & Francis.