Abstract: Different well-known gas permeation theoretical models such as Maxwell model, Bruggeman model, Lewis-Nielson model, Pal model, Felske model and modified Felske model has been discussed for prediction of the relative permeability of CO2 in Matrimid® 5218-Carbon Molecular Sieve (CMS) Mixed Matrix Membranes (MMMs). For evaluation of the theoretical models, experimental data of relative permeability for CO2 in Matrimid® 5218-Carbon Molecular Sieve (CMS) mixed matrix membrane were compared with the prediction of the theoretical models for the relative permeability of CO2 in ideal and rigidified interfacial morphology of the mixed matrix membrane. Comparison of those models was carried out based on the widely used model validation criteria including absolute average relative error percent and standard deviation. For the models evaluated under ideal morphology, the results showed a decrease in the absolute average relative error percent and standard deviation in the following order: Pal model > Lewis-Nielsen model > Maxwell model > Bruggeman model. For other models evaluated considering the presence of rigidified interfacial morphology, the absolute average relative error percent and standard deviation showed a decrease in the order, Felske model > modified Felske model. Hence, the modified Felske model was found to be in a better agreement with experimental data for prediction of relative permeability CO2 in Matrimid® 5218-CMS mixed matrix membrane.