The effects of hydration variables on the physical properties of the sorbents prepared from fly ash-Ca(OH)(2) mixtures were investigated and compared. It was observed that low fly ash/Ca(OH)(2) weight ratios can be appropriate when pressure hydration and alkali added atmospheric hydration techniques are used instead of atmospheric hydration. Pressure hydration fosters the formation of a sorbent reactive to SO2 from fly ashCa(OH)(2)-in a much shorter time than by atmospheric hydration. The sulphation capacities of the hydrated sorbents were also determined. Measured SO2 captures and Ca(OH)(2) conversion values of the hydrated sorbents were ranged between 1.43 and 3.61 mmole SO2/g sorbent and 28.22% and 68.37%, respectively. It was found that SO2 captures varied significantly depending on the physical and chemical properties of the hydrated sorbents. An empirical relation between the SO2 capture and surface area of the sorbents was obtained.