A series of Rh-Sn/SiO2 catalysts has been prepared by successive impregnation of SiO2 sol-gel (pH 5) with precursors chlorides of rhodium(III) and tin(II). Monometallic Rh/SiO2 and Sn/SiO2 samples were also prepared for comparison. The solids had been characterized by transmission electronic microscopy (TEM), electron diffraction (ED), temperature programmed reduction (TPR), H-2 chemisorption and X-ray photoelectron spectroscopy (XPS) techniques. The catalytic evaluation of crotonaldehyde hydrogenation was performed in liquid phase hydrogenation at atmospheric pressure. Only a slight increase in the metal particle size and significant rhodium coverage is produced by tin as it was found by TEM and XPS. Both Rho and Rhdelta+ species were detected in low content of tin catalysts, whereas a high proportion of tin in an oxidized state (close to 70%) in all the samples was found by XPS. ED studies allowed the detection of bimetallic phases, RhxSny and oxides of tin as SnO2. An important decrease in catalytic activity is produced by addition of tin, however, at the same conversion level, a significant enhancement in the selectivity to crotyl alcohol (CROL) was observed. The results are explained on the basis of an electronic effect produced by the oxidized tin species and RhxSny intermetallic phase that allow the polarization of the carbonyl group and inhibit the hydrogenation of C=C, respectively. The presence of these new species, modifies the nature of the active sites contributing to an increase in the selectivity to CROL due to electronic effects. However, at higher Sn/Rh, the activity drops significantly due to a decrease in the hydrogenation capacity and also due to the creation of surface acid sites, an important amount of byproducts, such as acetals and esters are obtained.