We have applied the electrocatalysis theory based on the Santos-Koper-Schmickler Hamiltonian to investigate the reactivity of nanostructures. A good agreement with experimental results has been obtained for monolayers of Pd on different substrates. The strain induced by the mismatch in the lattice constants of substrate and adsorbate is extensively discussed. We show that it is not the only effect for changing the electrocatalytic properties; also the specific chemical interaction between the monolayer and the substrate plays an important role. The catalytic properties of the nanostructures can be different for oxidation and reduction reactions. (C) 2009 Elsevier Ltd. All rights reserved.