Recent and ongoing research on Fischer–Tropsch catalysts for biomass conversion typically focus on the effects of impurities common in bio-derived synthesis gas, and also on the effect of different synthesis gas compositions expected from biomass gasifiers. Cobalt and iron catalysts share the sensitivity toward some, but not all of the impurities. The most profound difference is the strong negative effect of alkali, alkaline earth, and nitrogen containing compounds on cobalt catalysts while these impurities have a negligible or no effect on iron catalysts. CO2 appears to mainly act as a diluent in cobalt-based processes while iron catalysts respond differently to this component depending on catalyst design. In particular, iron catalysts containing Al2O3 as a structural promoter display a high stability, C5+ selectivity, and activity in CO2 rich synthesis gas.