Adsorption of benzene and cyclohexane on catalyst supports γ-Al 2 O 3 and catalyst pellets Pd/γ-Al 2 O 3 was studied from 393 to 453K over an adsorbate relative pressure range of 0.2–1.0. The corresponding adsorption isotherms, which were experimentally measured in the range of the relative pressure p/p 0 larger than 0.2, were considered to be type IV, and can be simulated by a simple adsorption model. The adsorption isotherm of benzene was similar to that of cyclohexane. Compared with the adsorption isotherm of benzene on γ-Al 2 O 3 , a similar one was obtained on Pd/γ-Al 2 O 3 except that the hysteresis loop appeared a little bit earlier. As far as adsorption of benzene on γ-Al 2 O 3 was concerned, only physisorption was involved. But when it came to Pd/γ-Al 2 O 3 , both chemisorption and physisorption occurred, and the chemisorption process facilitated the formation of monolayer, multilayer and capillary condensation in spite of the lower metal loading of the catalyst.