Process for the production of hydrocarbon blends with a high octane number by the hydrogenation of hydrocarbon blends, containing branched C.sub.8, C.sub.12 and C.sub.16 olefinic cuts, characterized by sending said blends, as such or fractionated into two streams, one substantially containing the branched C.sub.8 olefinic cut, the other substantially containing the branched C.sub.12 and C.sub.16 olefinic cuts, to a single hydrogenation zone or to two hydrogenation zones in parallel, respectively,only the stream substantially containing of saturated C.sub.8 hydrocarbons, obtained by the fractionation of the stream produced by the single hydrogenation zone or obtained by the hydrogenation zone fed by the fractionated stream substantially containing the branched C.sub.8 olefinic cut, being at least partly recycled to the single hydrogenation zone or to the hydrogenation zone fed by the fractionated stream substantially containing the branched C.sub.8 olefinic cut, and the hydrocarbon blend with a high octane number, obtained by the fractionation of the stream produced from the single hydrogenation zone or obtained from the hydrogenation zone, being fed by the fractionated stream substantially containing the branched C.sub.12 and C.sub.16 olefinic cuts.