The liquid-phase alkylation of phenol with tert-butanol in the presence of the H+ form of the zeolites with FAU, BEA, and MOR topologies was investigated. Over dried catalysts, tert-butyl phenyl ether is the main product of alkylation. The accumulation of water molecules on the catalyst surface suppresses this reaction. The irreversible C-alkylation of phenol becomes the main reaction only after an induction period. The catalytic activity and selectivity are controlled by the porous structure and acid properties of the zeolite. The three-dimensional interconnecting pore system of Beta and USY zeolites showed a higher catalytic activity than the monodimensional system of pores of the MOR zeolites. As concerns the catalytic selectivity, the USY zeolites were selective for the ortho-butylation, whereas BEA zeolites were the most efficient catalysts for the para isomer forming. (C) 2003 Elsevier Inc. All rights reserved.