The performance of different Ni/Mg-Al catalysts modified with Ce was evaluated in the catalytic steam reforming of aqueous fractions of bio-oil from biomass pyrolysis. The effects of several preparation methods for incorporating Ce as a modifier (co-precipitation, impregnation and direct thermal decomposition of the salt precursors), the Ce content (0-5 wt.%) and the feed streams (three different aqueous fractions from bio-oil) on the catalyst performance were examined, and it was found that the stability and activity of the catalysts were significantly influenced by all these factors. In general, the addition of Ce to a reference Ni/Mg-Al catalyst improved the overall carbon conversion to gas and the yield to H-2 as well as enhancing the catalyst stability in the steam reforming of aqueous fractions of bio-oils. The best preparation method was impregnation and the optimal Ce content was found to be 0.5 wt.%. Much higher initial carbon conversion to gas and initial H2 yields was obtained using bio-oils derived from pine than those derived from poplar. A very low coke formation, 103 mg C/(g of catalyst g of organics in the aqueous fraction reacted), was achieved using the optimized catalyst, 0.5 wt.% Ce prepared by impregnation. (C) 2017 Elsevier B.V. All rights reserved.