Abstract: The low-temperature (T = 2 K) optical spectra (transmission, reflection and luminescence) of a compositionally graded CdS_1 – xSe_x/CdS heterostructure with a low Se content near the sample surface were studied. The Morse potential model of the near-surface exciton potential well is shown to be in a good agreement with the experimental data on the excitonic reflection and makes it possible to identify the radiative recombination channels of free and localized excitons in the structure under study.