The immobilization of silver nanoparticles onto the polystyrene surface was successfully carried out by novel preparation route involving polyol process for the first time in our previous study [J.M. Lee, D.W. Kim, Y.H. Lee, S.G. Oh, Chem. Lett. 34 (7) (2005) 928]. In this study, in order to obtain better insight about the reaction process, the silver-polystyrene nanocomposite particles were prepared by modified polyol process in the presence of four poly(vinylpyrrolidone) polymers (PVP K12, PVP K15, PVP K30 and PVP K90) with the same structure but different molecular weights. In addition, the effect of PVP K15 concentration on the formation of silver-polystyrene nanocomposite particles was investigated. On the basis of the experimental results, the effect of the PVP molecular weight and concentration on the formation of composite particles was discussed in detail. This research can contribute in delineating the fundamental mechanism of composite particle formation and extending the use of this process to the new application areas. (C) 2008 Published by Elsevier B.V.