Photoluminescence (PL) properties of Sm-doped ZnSSe/ZnS multi-quantum wells were studied. The PL spectra were dominated by red-emission around 651 nm due to intra-atomic 4f-4f ((4)G(2/5)-H-6(9/2)) transition of Sm3+. It was found that the PL intensity significantly increased and the peak position shifted to longer wavelength with decreasing well width. A significant enhancement of the PL intensity can be interpreted as an increase of the energy transfer probability from quantum wells to the Sm3+ ions. A novel material which has a high efficiency of radiative recombination is suggested.