New CoMo/Zn-Al mixed oxide catalysts were synthesized, characterized and tested in the HDS reaction of thiophene. Catalytic supports were synthesized by using variable (Al)/(Al + Zn) mol ratios from 0.0 to 1.0, then, these supports were calcined up to 450 degrees C and finally impregnated with Mo and Co, and calcined at 450 degrees C again. Before impregnation, these solids were characterized by XRD and FT-IR, and after impregnation, by BET surface area measurements and temperature programmed reduction (TPR). Results showed that the hydrotalcite phase is formed between 0.20 and 0.33 (Al)/(Al + Zn) mol ratios. At increasing Al content, an Al2O3 phase (beta-Al2O3) emerges together with the hydrotalcite phase which diminishes as Al content increases. Results corresponding to the thiophene HDS reaction showed a catalytic activity maximum at 0.25 ratio; then, the catalytic activity decreased with Al content. These results could be associated with an optimum combination of Al and Zn oxides in which their properties are complemented.