Many mass transfer kinetic models are used to study varying pressure steps of a pressure swing adsorption (PSA) cycle. namely pressurization and blowdown steps. It is shown that the choice of an appropriate model to account for intra-particle diffusional limitations is essential to simulate accurately PSA processes. It has been demonstrated that, besides mathematical approximations (parabolic profile within the particle), a very important factor that can affect simulation results remarkably is the correctness of the mass transfer kinetic model when regarded as being a mass balance for the adsorbent particle. In fact, neglecting intra-particle gas phase leads to erroneous simulations. Some models widely used in the literature, such as the classic linear driving force (LDF) and the solid diffusion models prove inadequate. It is recommended to use pore diffusion model as well as a new version of the solid diffusion model to get reliable predictions.