The hydrogenation of crotonaldehyde over a series of titania supported PtNi catalysts was investigated. Pt/TiO2 had the highest activity to hydrogenate the\(C = O\) bond of crotonaldehyde. With the addition of Ni to Pt the activity for carbonyl group hydrogenation decreased, while that for the\(C = C\) bond hydrogenation increased. Two different types of sites were established to be active for\(C = O\) bond hydrogenation, located at (i) the Pt-TiO2 interface and (ii) the PtNi bimetallic phase. For the Pt-TiO2 interface the presence of accessible Tix+ cations in close distance to Pt and for the PtNi phase a slightly positively charged Ni on the surface of these alloy particles were concluded to be responsible for the enhanced selectivity to crotylalcohol. The hydrogenation of the\(C = C\) bond occurs mainly on the “clean” metal surfaces of Ni and Pt.