Due to stringent environmental regulations, the reduction of aromatic compounds present in diesel fuel, precursors of particulate matter, is becoming one of the most important technologies in petroleum refining industries. However, the high quantity of nitrogen and sulfur compounds limits the use of catalytic processes. In this work Pt and Pd catalysts supported on alumina modified with rare earth oxides (Ce and Pr) were prepared, characterized by XRF, XRD, UV-vis-DRS and XPS, and tested in the hydrogenation of tetralin reaction, in the presence of different concentrations of thiophene. The results showed that the use of a Pr-modified alumina support enhanced the tolerance of the Pt/Al2O3 catalyst to thiophene. The addition of a second metal, Pd, despite a loss in activity, increased tolerance to this poison. The combination of both promoters exhibited a synergic effect, as the bimetallic catalyst supported in the Pr-modified alumina showed a very low sensitivity to thiophene, up to 2600 ppm, explained by the electron-deficiency of the metallic Pt. (C) 2007 Elsevier B.V. All rights reserved.