The influence of the shape/surface structure of Pt nanoparticles on the selective hydrogenation of crotonaldehyde and cinnamaldehyde has been studied. (I 11) and (100) preferentially oriented Pt nanoparticles (10 nm) as well as polyoriented Pt nanoparticles Q nm) were synthesized, characterized (by TEM, cyclic voltammetry and adsorption microcalorimetry) and their catalytic properties evaluated. TEM analysis provided information about the size and shape of the 111 nanoparticles, whereas cyclic voltammetry allowed gaining qualitative and quantitative information about their surface structure. Thus, small Pt nanoparticles (approximate to 3 nm) were revealed to have a polyoriented surface, containing high ratio of corner and edges atoms to terrace atoms, whereas large Pt nanoparticles (approximate to 10 nm) were shown to have larger Pt domains with (100) and (111) surface structures. Microcalorimetric results for CO adsorption showed higher values of initial heat for polyoriented Pt/C compared to preferentially oriented samples, thus accounting for a higher amount of highly unsaturated surface platinum atoms for Pt/C, in agreement with cyclic voltammetry. The catalytic performances of the samples showed a strong structure-sensitive character for both reactions, with TOF values following the trend Pt(100)/C > Pt(111)/C > Pt/C. Moreover, Pt(111)/C showed higher selectivities to unsaturated alcohol than Pt(100)/C and Pt/C samples. (C) 2007 Elsevier Inc. All rights reserved.