Zeolites with various silicon to aluminum ratios usually exhibit polar and nonpolar adsorption behavior depending on the degree of dealumination. The objective of the present study was to show the influence of the surface polarity on the adsorbate phase composition containing a polar and a nonpolar component : toluene and 1-propanol, respectively. Such systematic investigations should help to understand the significance of some adsorbent parameters, such as the surface heterogeneity. This basic knowledge is important for the development of improved models for the prediction of multicomponent adsorption equilibria.