Monodisperse polymer particles composed of polystyrene (PS) and poly(1,6-hexanedioldiacrylate) were prepared via one-step seeded polymerization using PS as seed particles. For the study, the effects of the molecular weight of seed polymer particles, the ratio of the absorbed hexanediol dimethacrylate (HDDA) to the seed polymer particles (swelling ratio), and the seeded polymerization rate on the surface morphology of poly(St-HDDA) particles were investigated. It was observed that the crater-shaped defect was at the surface of poly(St-HDDA) particles, independent of the molecular weight of seed polymer, and swelling ratio. But its surface morphology could be controlled by changing the rate of the seeded polymerization. (c) 2007 Wiley Periodicals, Inc.