Surface states and quantum-well states in thin metallic films are investigated within the framework of a nearly-free-electron (NFE) model and an effective-mass model by employing the Green's-function matching method. Applying the latter to Ag/Au(111), which is studied by angle-resolved photoemission, yields the edge parameters of the Ag sp band, viz., E(L'₂)=-0.35 eV and the effective mass m*=-0.19. The binding energies are obtained as a function of the film thickness. The NFE model with free-electron mass yields the best coincidence with the experimental data.