Three cation complexes: [Pt(NH 3 ) 4 ] 2+ , [Pt(NH 3 ) 2 (H 2 O) 2 ] 2+ and [Pt(H 2 O) 4 ] 2+ were used for the preparation of 0.6 wt.-% PtHY catalysts. The platinum dispersion depended on the platinum complex used as a precursor and, for a given complex, on the conditions of activation. The platinum dispersion of the catalysts prepared from the tetra-aquo platinum complex was very low, but this could be related to the great lability of the water ligands. It was also this lability which explained why the platinum dispersion was about twice as low for PtHY catalysts prepared from the diaquo-diammine complex than for those prepared from the tetra-ammine complex. However in the case of the two latter complexes, the activation conditions influenced the platinum dispersion in the same way: a highly marked effect of the calcination conditions and a small effect of the subsequent treatment under hydrogen flow. The behaviour of the PtHY catalysts for the bifunctional transformation of n-heptane did not depend on the platinum precursor. The activity and the selectivity of these catalysts depended only on their hydrogenating activity.