ZnS nanoparticles @ the channels of a mesoporous silica CMI-1 have been prepared by using a quite simple method and their photolurninescent properties have been studied. Characterization results confirm the presence of ZnS inside the material. PL spectrum of the nanocomposite shows an excitonic emission from bulk ZnS while an important blue-shifted emission attributed to quantum size effect of extremely small ZnS nanoparticles is also revealed. These interesting photoluminescent properties have been correlated with the surface modification and the interaction between ZnS nanoparticles and mesoporous surface. The present findings should lead to potential applications in optoelectronics and help to design the light-emitting systems and laser generators. (c) 2006 Elsevier B.V. All rights reserved.