The impact of nanciparticle size effects on the heterogeneous catalytic kinetics is discussed accounting for changes in chemical potential upon adsorption. Two-step and Christiansen sequences, as well as Langmuir-Hinshelwood mechanisms are considered. showing that for catalytic reactions over nanoparticles not only the rates, but also reaction orders can be different from those obtained for large nanoclusters. Theoretical considerations are presented for selectivity dependence in parallel and consecutive reactions on the nanoparticle size when there are changes in chemical potential with adsorption. Comparison with experimental data for Fischer-Tropsch synthesis by cobalt supported on carbon nanofibers, as well as for crotonaldehyde hydrogenation over gold supported on TiO2 illustrates applicability of the thermodynamic analysis for the explanation of nanoparticle size effect on kinetics. (C) 2008 Elsevier Ltd. All rights reserved.