Ozone concentration profiles have been measured in a 0.254 m I.D. circulating fluidized bed reactor with impregnated FCC as catalyst. The axial ozone profiles show that deviations from plug flow are significant. The radial profiles show that ozone concentration is lower in the wall region than in the core region, consistent with observations of wall-flow of solids. The pseudo-homogeneous CSTR and plug flow models were used to estimate the reactor effectiveness factor from the experimental data with gas velocities in the range of 2 to 8 m s-1 and solids circulation rates of up to 200 kg m-2 s-1. The results show that the effectiveness factor drops as Damkohler number kr′ increases and is also lower at lower gas velocities.