A new concept is advanced to explain some effects of oxygen-containing groups of the carbon surfaces on the dispersion of Pt/C catalysts prepared through the adsorption of H2PtCl6 onto porous carbon powders followed by the reduction with H-2. These groups alter the electrochemical properties of the support and, therefore, influence the nature and amount of the adsorbed catalyst precursors formed during a redox reaction between the carbon surface and H2PtCl6, that reflects on the dispersion of Pt/C. A way to account for their impact on platinum dispersion is offered. It allows revising and uniting many literature data related to this problem.