Hydrogenation of tetralin was used to modelize the hydrogenation of aromatic compounds in gasoils. This reaction was carried out under a 5 MPa hydrogen pressure, at 300 degrees C, in the presence of hydrogen sulfide. Before reaction, the Ru on KY zeolite catalyst was presulfided in situ at 400 degrees C either by a H2S/H-2 mixture, or by dimethyl disulfide in n-heptane. The catalyst sulfided by dimethyl disulfide was 3 times less active than that sulfided by H2S, due to coking during sulfidation. Another type of carbonaceous deposit was formed during the tetralin reaction, the nature and the amount of this deposit was not depending on the sulfidation method.