A systematic study of both acid and steam dealumination of mordenite has been carried out aiming to obtain a mordenite featuring high acid strength active sites along with a secondary mesoporous system, in order to maximize both catalytic performance and time-on-stream stability of the material in solid-acid catalyzed alkylation of benzene with 1-dodecene. Detailed assessment of the textural (XRD, N-2 adsorption-desorption) and acid (FTIR of pyridine adsorption) properties of the obtained materials was per-formed. It has been found that catalysts obtained by combined steam dealumination and acid washing show a dramatic increase in the intrinsic activity and a significantly lower tendency to suffer deactivation when compared to the parent zeolite and samples obtained by acid treatments. This improved behaviour of the steam-treated sample is attributed to its increased mesoporous surface area, lower acid sites concentration and less hydrophilic surface. (c) 2006 Elsevier B.V. All rights reserved.