The possibility is considered of using a surface modified to have pits of certain shape and size to effect a selective adsorption of molecules thereon. A theoretical analysis of the thermodynamics and the kinetics of the selective adsorption of molecules on the modified surface is performed. A "surface modification efficacy parameter", gamma, is suggested, equal to the ratio of the concentrations of molecules in the pits and on the unmodified surface. The expressions for the parameter gamma are derived with the help of both the thermodynamic and the kinetic approaches. The parameter gamma is estimated with the help of computer simulation by considering as an example the adsorption of argon atoms and acetylene and benzene molecules in the pits of the graphite surface.