The equilibrium parameters for the adsorption of Mo(VI) on gamma -Al2O3 and of Co(II) and PF(IV) on MoO3/gamma -Al2O3 were determined. The adsorption isotherms were performed from aqueous solutions of the corresponding precursors on two different alumina supports. According to the classification given by Giles, L-type-shaped, subgroup 2, adsorption curves were found for the system Mo on gamma -Al2O3, L-type, subgroup 1, for the Pt on MoO3/gamma -Al2O3, and S-type for Co on the MoO3/gamma -Al2O3 system. Numerical calculations were carried out for all the isotherms to find the equilibrium parameters. These constants are being used to model the development of Pt, Co, and Mo profiles on MoO3/gamma -Al2O3 or gamma -Al2O3 extrudates, respectively which belong to the new generation of noble-metal-MaO(3)/gamma -Al2O3-supported catalysts to be used in oil-refining processes,