The influence of ad-atom adsorption on the kinetics and mechanism of the reduction of nitro, nitroso compounds and dioximes is discussed. Ad-atom layers of Pb, Tl, Bi, Cu, etc., deposited in the underpetential region, have a strong influence on the performance of noble metal electrodes for the nitro and nitroso group electroreduction as well as the reduction of quinone  dioximes. The ad-atom layers improve the catalytic activity and the catalytic selectivity of these electrodes. Studies on ad-atom modified single crystal electrodes revealed that the kinetics and mechanism of the reduction of nitro compounds could be correlated to the superlattice structure of the metal adlayers.