Promoters of metal catalysts play an essential role in the hydrogenation of unsaturated bonds, such as in carbonylic compounds. This promotion is a key to a high selectivity to unsaturated alcohols in hydrogenation of alpha,beta-unsaturated aldehydes. Analysis of the information available in the Literature on the adsorptions through the C=C and C=O groups, respectively, together with the information on the catalytic behaviour of the promoter-free and promoted catalysts, allows us to suggest a model of surfaces active in selective hydrogenation of unsaturated aldehydes.