Nanoprecipitation represents an effective method for the production of polymeric nanoparticles This technique was used to prepare nanoparticles from solutions of poly(methyl methacrylate) and its copolymers Since the regulation of main parameters like particle size, particle size distribution, and molar particle mass is very important for future applications, the stable nanoparticle dispersions were examined by scanning electron microscopy, velocity sedimentation, and dynamic light scattering, whereby advantages and disadvantages of each characterization techniques are discussed Poly-dispersities of particle size distributions are determined by the ratio of d(w)/d(n), where d(w) and d(n) are weight- and number-aver-age diameters, respectively The particle characteristics strongly depend on the chemical structure of the polymers and the way of preparation and, therefore, vary in the studied cases in the range of 6 < d(w) < 680 nm, whereas the polydispersity index d(w)/d(n) changes in the range of 1 02 to 1 40 It is shown that nanoparticles in a desirable size range can be prepared by solvent-nonsolvent methods (dialysis technique or dropping technique) (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A Polym Chem 48 3924-3931, 2010