In the study of a reaction on a heterogeneous catalyst, external and internal mass diffusion play an important role since they can have an inherent affect on the kinetics of the reaction. Therefore, in the study of intrinsic rates of reaction, the effects of external and internal mass diffusion must be eliminated or considered prior to proper kinetic studies. In this study, the effects of external and internal mass diffusion on the propane dehydrogenation reaction over a Pt/Sn catalyst were investigated. Some experiments were performed in a laboratory scale setup and the required data was gathered. The rate of reaction was considered to be first order based on propane. External diffusion was studied using Mears' criterion and internal diffusion was investigated by the Thiele Module and the Internal Effectiveness Factor, based on experimental data.