The possibility of fabricating quantum dots under Volmer-Weber growth mode is investigated. Layers of ZnSe/ZnS were grown by metalorganic chemical vapor deposition on both Si and GaAs substrates. The images of surface morphology, taken by atomic force microscopy, showed that the layers were grown in three-dimensional islands. Blueshift was observed in the photoluminescence spectra up to room temperature for these samples. This blueshift was shown to originate from the ZnSe islands. The effect of ZnSe growth duration was investigated. It was found that the blueshift increased with shorter ZnSe growth durations, but this near band gap emission disappeared when the ZnSe growth duration was longer than 5 s. Effects of quantum confinement and strain were considered to resolve the origin of the blueshift. Our result suggests that carrier confinement plays a dominant role.