The reaction of steam with ethanol, ethanol + phenol, ethanol + phenol + tetrahydrothiophene, methanol + phenol, methanol + naphthalene and methanol + phenol + naphthalene mixtures in the vapour phase has been studied over catalysts based on Ni/Al2O3. The main conclusion is that Ni-alumina based steam reforming catalysts are effective for steam reforming of phenol and naphthalene even mixed each other and with light alcohols at T > 973 K in the absence of sulphur. However, at lower temperatures and when deactivated by sulphur they may become active catalysts in converting these molecules in a number of polyalkylphenols which represent low-volatility secondary and tertiary tars.