Radiopaque micron-sized non-cross-linked polystyrene/poly(2-methacryloyloxyethyl(2,3,5-triiodobenzoate)) particles of narrow size distribution were prepared by a single-step swelling of uniform polystyrene template microspheres with emulsion droplets of methylene chloride containing the initiator benzoyl peroxide and the iodinated monomer 2-methacryloyloxyethyl( 2,3,5-triiodobenzoate), followed by the polymerization of the monomer within the swollen template particles at 73 C. Radiopaque micron-sized uniform cross-linked polystyrene/poly( 2-methacryloyloxyethyl( 2,3,5-triiodobenzoate)- divinylbenzene) composite particles were prepared similarly with emulsion droplets of methylene chloride containing divinylbenzene, in addition to the initiator and the iodinated monomer. Radiopaque micron-sized uniform cross-linked poly(2-methacryloyloxyethyl( 2,3,5-triiodobenzoate)divinylbenzene) particles were formed by dissolving the template polystyrene polymer belonging to the former cross-linked composite particles. Characterization of these novel radiopaque polymeric particles was performed by methods such as FTIR, TGA, DSC, SEM, XPS, elemental analysis, and light microscopy. The influence of the weight ratio [2-methacryloyloxyethyl( 2,3,5-triiodobenzoate)]/[polystyrene] and [2-methacryloyloxyethyl( 2,3,5-triiodobenzoate)]/[divinylbenzene] on the bulk and surface properties of the non-cross-linked and cross-linked particles, respectively was elucidated. The radiopacity of these iodinated particles was demonstrated by an imaging technique based on X-ray absorption usually used in hospitals. These novel radiopaque particles may be used for different X-ray imaging needs, e. g., blood pool, body organs, embolization, dental composition, implants, protheses, and nanocomposites.