Ca sorbents with a grain size 90-400 pm were placed in combustion furnace and heated at 850-1000 degrees C in CO2 and O-2-contg. atm. in amts. of 20/80, 50/50 and 70/30 by vol. resp. and 3000 ppm of SO2. The degree of calcination and sulfation of the sorbents during the process was detd. The indices of reactivity and absolute sorption were calcd. The sorbent porosity was detd. by using a Hg porosimeter. Open, intra and intergranular porosity and mean diam. of sorbent particle were evaluated. The effective simultaneous calcination and sulfation were closely related to changes in porosity of sorbent. The optimum temp. for the capture of SO2 was 900-950 degrees C in the presence of flue gas contg. 70% CO2 and 30% O-2.