This paper presents a comparative study of Fischer-Tropsch synthesis in single channel milli-fixed bed, conventional centimetric fixed bed and slurry stirred tank reactors. In the three reactors, the catalytic measurements were carried out with the same conventional platinum-promoted alumina supported cobalt catalyst at 493 K and 20 bar using a stoichiometric syngas ratio (H(2)/CO = 2). The single channel milli-fixed bed reactor displays a higher initial Fischer-Tropsch reaction rate than the conventional centimetric fixed bed reactor. This effect was assigned to a better temperature control and less significant catalyst deactivation during the startup of the single channel milli-fixed bed reactor. The slurry stirred tank reactor shows much lower hydrocarbon productivity than the milli- and centimetric fixed bed reactors, which is probably due to incomplete catalyst reduction. A considerable catalyst deactivation due to the uncontrolled temperature hike can occur during the reactor startup in the conventional centimetric fixed bed reactor. The slurry stirred tank and milli-fixed bed reactors show similar apparent deactivation behavior. (C) 2011 Elsevier B.V. All rights reserved.