The effect of modification of γ-aluminia support by Cr2O3 on physical and catalytical properties of supported rhodium catalysts was investigated. Various techniques were used for characterization of catalysts: porosimetry, diffusion and permeation measurements, determination of surface OH groups, temperature-programmed reduction and catalytic behaviour in steam dealkylation of toluene. Using the transport parameters determined for pelleted catalysts the effect of internal diffusion on the reaction was predicted and compared with experiments.