The catalytic slurry bubble column reactor (SBCR) has been proven to be a very effective reactor and is widely used in the chemical industries. In this study, by means of mathematical modeling of Fischer-Tropsch synthesis (FTS) in a bubble column slurry reactor, a comparison of single- and two-bubble class gas-liquid recirculation models was made. Detailed kinetics expressions for the FTS and water gas shift reactions have been considered. A selectivity model combined with slurry bubble column reactor hydrodynamics and the multicomponent vapour-liquid equilibrium (VLE) model have been applied to predict the distribution of olefins and paraffins in the products. The experimental results taken from the literature have been compared with simulation results from two mechanistic reactor models: single-bubble class and two-bubble class model, which indicates that in some operation conditions the two-bubble class model (TBCM) dose not present additional advantages over SBCM. (C) 2009 The Institution of Chemical Engineers. Published by Elsevier B.V, All rights reserved.