The adsorption of benzene over sites I, II and III of Cu- and Na-exchanged zeolite-Y, has been studied using the energy profiles for the host-guess interaction, and electronic descriptors of reactivity such as the electronic chemical potential and a local sigma(k) index recently defined. Both, the energy and the reactivity index based models consistently complement each other to give a correct interpretation of the reactivity and selectivity patterns experimentally established for these systems. (C) 2003 Elsevier, B.V. All rights reserved.