The surface and catalytic properties in the vapor-phase hydrogenation of crotonaldehyde on Rh/TiO2 has been studied. It was found that a partial reduction of the support produces a surface decoration of the metal component. Thus, interfacial sites are created, which are responsible of an increase in the selectivity to crotyl alcohol, via enhancement of the polarization of the C=O bond. Photoelectron spectra revelead that rhodium is in different oxidation states, with a contribution of ca. 20 % Rhdelta+ and 80 % Rh-0 species for LTR catalyst and only a slight increase of Rhdelta+,for HTR catalyst. TEM studies revelead that Rh has metal particle size close 3 nm with small increases in the catalyst reduced at high temperature. DRIFTS essayed carried out under reaction conditions allowed to identify crotonaldehyde species strongly adsorbed through the C=C bond and weakly coordinated through both the C=C and C=O bonds. After reduction at 723 K an increase in the peak at 1660 cm(-1) ascribed to an interaction between the carbonyl group and the surface, was observed. This peak seems to be stabilized at interfacial Rh/TiOx sites. The deactivation in crotyl alcohol formation can be ascribed to the generation of strongly chemisorbed asymmetric carboxylate, species detected by band at 1740 cm(-1). This band grows at expense of crotonaldehyde O s - bonded intermediate chemisorbed on coordinatively unsaturated sites (Lewis acid sites) responsible of the crotyl alcohol obtaintion (detected by a band at 1653 cm(-1)). Additionally, a small band at 2068 cm(-1) assigned to CO adsorbed on transition metals, which increases with time on-stream may explain the deactivation of the catalysts in flow systems.