Adsorption of H2PtCl6 onto a carbon support followed by reduction of the adsorbed platinum species with H-2 at 250 degrees C leads to PVC catalysts, which show universal volcano-like dependence of platinum dispersion on the metal loading in the range from 0.01 to 0.55 mu mol (Pt/m(2) (S-BET) when highly disordered carbons, namely, active carbons and carbon blacks, are used as supports. The maximal dispersion D(CO/Pt) = 0.8 is attained at 0.18 mu mol (Pt)/m(2) (S-BET). With other factors being equal, the dispersion of platinum supported on carbons with a more regular crystal structure, especially Sibunit-type supports, proves to be the highest and independent of the metal loading. The differences between the two groups of carbon supports are explained by the differences in the state of the adsorbed platinum precursors.