This work describes the effect of the support (TiO2, hybrid 2TiO2-SiO2, SBA-15 and SBA-15 decorated with TiO 2 particles) on the catalytic activity of ZnNi catalysts in the gas-phase hydrodeoxygenation (HDO or O-removal) of phenol and the liquid-phase hydrodearomatization (HDA) of synthetic diesel. These reactions are representative of the two major challenges of the hydrotreating unit embedded in a sustainable refinery: (i) decreasing oxygen content of bio-oils (produced in the pyrolysis of lignocellulosic biomass); and (ii) decreasing aromatics content in diesel. The fresh and deactivated catalysts were characterized by XRD, N2 adsorption-desorption, TPR, MS/TPD-NH3, XPS, SEM, HRTEM and coke combustion. Under steady-state conditions, the ZnNi catalyst supported on SBA-15 decorated with TiO2 particles displayed the highest activity in the hydrodeoxygenation of phenol (selectivity toward deoxygenated products > 95%) whereas the ZnNi/SBA-15 catalyst displayed the highest activity in the hydrodearomatization of synthetic diesel. It has been shown that dispersion of the active ingredient is favoured on the SBA-15 substrate. The relationship between structure and activity demonstrated that HDO and HDA reactions require optimized metal dispersion and acid function, metal dispersion being more important for HDA than for HDO reactions. © 2012 The Royal Society of Chemistry.