Support plays an important role in the preparation of highly active and selective bioethanol steam reforming catalysts since it helps in the dispersion of metal particles and enhances its activity via metal-support interactions. The singular structure of zeolites makes these materials attractive to be used as supports for dispersing active metal phases. We have explored the activity, selectivity, and stability of Ni metal particles supported over a modified commercial Mordenite in the steam reforming of bioethanol. Commercial Mordenite has been previously modified in order to generate mesoporosity and produce good positions for the stabilisation of Ni metallic particles. The presence of mesoporosity has allowed preparing highly active catalysts for the steam reforming of bioethanol. The addition of alkaline metals (Na) has been also studied and it has been found that Na presence improves significantly the selectivity to hydrogen while decreases the coke deposition. A complete characterization of Ni-based modified Mordenite catalyst has been carried out (DRX, BET area, TPR and TEM) and interesting relationships between its catalytic performance and physico-chemical properties have been found. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.