The effect of pore size distribution of zeolite on the multicomponent adsorption equilibrium is studied. All species compete locally for a given pore and this can be described by the extended multicomponent Langmuir isotherm. The size exclusion effect is taken into account in the competition of different species for a given pore so large molecules have less degree of accessing available pores. The pore size is related to the adsorbate-adsorbent interaction energy by the Lennard-Jones potential. The isotherm parameters extracted from single-component data fitting are used to predict multicomponent adsorption equilibrium. When validated with binary experimental data of CO2, H2S and propane in H-mordenite, collected by Talu and Zwiebel (1986), this model provides better results than a previously proposed heterogeneous model based on a uniform energy distribution and a local IAST (Hu and Do, 1995).