Two groups of Ni catalysts, supported on γ-Al2O3 and MCM-41, respectively, were prepared by incipient wetness impregnation and tested for their influence on the pyrolytic decomposition of cellulose. A thermogravimetric analyser coupled with a mass spectrometer (TG–MS) was used to examine the influence of catalyst loading, support material, and the presence of additional water vapour on H2 selectivity. Normalization of the raw MS data enabled semi-quantitative analysis of the product gas distribution, which facilitated reliable comparison between different experimental conditions. Catalysts were characterized by BET, XRD, SEM/EDX and TEM. MCM-41 supported Ni significantly elevated the yield of H2 and total gaseous product, both under Ar and with the injection of additional water vapour when compared with the γ-Al2O3 support. 15wt.%Ni/γ-Al2O3 and 5wt.%Ni/MCM-41 were identified as the most active catalysts from the two groups with regards to H2 selectivity and yield.