A study is reported of the effect of exciton localization by solid-solution compositional inhomogeneities near the crystal surface, which gives rise to new unusual features in the optical excitonic spectra. These features, observed in exciton reflectance spectra of CdS_1-xSe_x with low Se contents (x∼0.01), were studied in the 4.2-200-K temperature range. Models of the localizing excitonic potentials providing an adequate description of the experimental reflectance spectra were found. Nonlinear model potentials taking into account the diffusion mechanism at the onset of structural inhomogeneities and the state of the real crystal surface were invoked. The shape of the additional structure in the reflectance spectra was found to be very sensitive to the type and parameters of the near-surface potential well.