Fischer-Tropsch synthesis (FTS) with biomass-derived syngas was performed using both iron-based 100Fe/6Cu/4K/25Al catalyst and ruthenium-based 5 % Ru/SiO2 catalyst. During FTS, different concentrations of steam were co-fed with the biomass-derived syngas to promote the water gas shift reaction and increase the H-2/CO ratio. On Fe-based catalysts the increase in steam concentration led to lower conversion, while deactivation is not observed on Ru-based catalysts. XRD of the spent iron-based catalyst showed the oxidation of iron carbides. Adding steam inhibited surface carbon deposition, as measured by temperature programmed hydrogenation. The iron carbide phase could be re-carburized by flowing CO. The addition of steam had different effects on these two catalysts. Fe-based catalyst showed significantly lower methane selectivity and greater C5+ hydrocarbon selectivity, while on the Ru-based catalyst, adding steam only showed slightly decreased methane selectivity. [GRAPHICS]