This paper investigates the intensification of Fischer-Tropsch Synthesis in two types of three-phase catalytic reactors: slurry bubble columns and multi-tubular fixed beds. A simple mathematical model is used to analyse the effect of structuring on the C5+ productivity of these two types of reactors. The results of the model show that decreasing the liquid axial dispersion coefficient with a factor 4 in a slurry bubble column considerably enhances the production of C5+. On the other hand in a fixed bed reactor a similar improvement is obtained when the heat transfer coefficient is improved with a factor 2.5 and the diffusion length in catalyst particles is decreased with a factor 2. Both reactors show a potential improvement in productivity per reactor volume; 20% in the slurry bubble column and 40% in the fixed bed reactor. (C) 2012 Elsevier B.V. All rights reserved.