By using the numerical discretization method within the effective‐mass approximation, we have theoretically investigated the exciton‐related Raman scattering, interband absorption and photoluminescence in colloidal CdSe/CdS core/shell quantum dots ensemble. The interband optical absorption and photoluminescence spectra have been revealed for CdSe/CdS quantum dots, taking into account the size dispersion of the ensemble. Numerical calculation of the differential cross section has been presented for the exciton‐related Stokes–Raman scattering in CdSe/CdS quantum dots ensemble with different mean sizes.