Simultaneous CO2/SO2 capture characteristics of three limestones were investigated in a pilot scale fluidizedbed reactor. For each of these sorbents, the measured CO2 capture capacity decreased as the number of cycles increased and as the SO2 concentration increased. On the other hand, the SO2 capture increased with the number of cycles and the SO2 concentration. The total calcium utilization decreased as the number of cycles increased, but the effect of SO2 concentration on the total calcium utilization depended on the sulfation pattern of limestone. For one limestone ( with unreacted- core- type sulfation), the total calcium utilization decreased with increasing SO2 concentration. However, for the other two limestones ( with uniform- type sulfation), the total calcium utilization was almost independent of SO2 concentration for the range investigated. The results show that SO2 reduces the CO2 capture capacity of limestone and indicate that the sulfation patterns affect the CO2 capture capacity.