The effect of gallium in W/Ga(x)-␥-Al 2 O 3 catalysts was investigated in the hydrodesulfurization of dibenzothiophene. The ␥-Al 2 O 3 carrier was modified by the gallium addition prior to W impregnation and further calcination at 723 K. An electrophoretic study was carried out on the calcined Ga samples at 0, 0.29, 0.55, 0.84, 1.09, 1.43, 1.71 and 2.22 wt.% of Ga and it indicated that Ga addition affected significantly the surface of alumina. The presence of at least two gallium species was proposed, at low gallium content GaAl 2 O 4 species decreased the isoelectric point (IEP) and probably the formation of Ga 2 O 3 at higher contents increased again the IEP. Raman spectroscopy showed that the gallium incorporation had a strong effect in the formation of WO x species at the surface of catalysts. The highest amount of irregular WO x particles calculated by the Raman (O W O + W O)/W-O-W band intensities ratio was found on the W/Ga(1.09)-␥-Al 2 O 3 catalyst. The presence of gallium induced higher activity on the dibenzothiophene hydrodesulfurization reaction in all catalysts tested. The highest Raman ratio and the highest activity were found for the W/Ga(1.09)-␥-Al 2 O 3 catalyst, suggesting that better dispersed W species could be responsible for the highest HDS activities.