The one-dimensional cluster model and the ore-annulus model are examined based n existing correlations. The core-annulus model is found to give reasonable agreement with ozone decomposition, data when the effective interphase mass transfer rate constant is equal to about 0.1 1/s, which is one order smaller than the reported values based on gas tracer tests. The prediction from the core-annulus model that the reactor performance decreases with increasing, the riser diameter is found to be inconsistent with limited experimental data The one-dimensional cluster model predicts that a riser reactor performs very close to the pseudo-homogeneous plug flow reactor because of the high mass transfer rate between the clustler and the dilute phase. The improvement of model predictions lies in the better characterization of the cluster shape size and the mass transfer rate between the cluster and the dilute phases.