Sorbents for SO2 removal from flue gas were prepared by slurring fly ash and Ca(OH)(2). Four fractions of different particle sizes were obtained by sieving and by grinding. These fractions were characterised by determining mean diameter values, the BET specific surface area and the pore size distribution and tested in the desulfurization reaction for 5 and 60 minutes at low temperature in order to relate the particle size and structural properties of the sorbents to the desulfurization ability. Fractions obtained by sieving showed similar BET specific surface area values and pore size distribution to each other. The conversion values at both reaction times were higher for fractions with the smaller particle size. Fractions obtained by grinding exhibited different structural properties depending on the reduction procedure. These fractions with smaller mean particle sizes than those obtained by sieving, showed smaller conversion values. Results indicated that the influence of the particle size is showed only for sorbents with similar pore size distribution. A quantitative relationship between pore filling (due to the calcium sulfate formed) and conversion values has not been found.