This paper presents the contribution of hydrogen spillover to the hydrogenation of naphthalene over Pt/RHO catalysts. Platinum supported on RHO zeolite was prepared by adding a Pt precursor to the synthesis gel of RHO zeolite. Pt/RHO catalysts were characterized by XRD, TEM, TPR and XPS. The hydrogenation activity was tested using 1-hexene, 1-cyclohexene and naphthalene as model compounds. XRD and TEM results indicated that incorporating Pt precursors into the synthesis gel did not affect the crystal structure and the morphology of the RHO zeolite. TPR, XPS and hydrogenation tests revealed that Pt particles were located in both RHO cages and intrazeolite spaces. In Pt/RHO containing lower levels of cesium, a small amount of Pt was also located on the external surface of the zeolite. The contribution of hydrogen spillover over hybrid Pt/RHO_H-Y zeolite catalysts was examined in naphthalene hydrogenation. Naphthalene conversion increased from 21% over a Pt/RHO catalyst to 91% over Pt/RHO diluted with H-Y zeolite, clearly demonstrating the positive effect of hydrogen spillover on the hydrogenation reaction. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.