The synthesis by oxidative polymerization of well-defined poly(3,4-ethylenedioxythiophene) (PEDOT) nano-objects in the presence of modified and unmodified poly(N-vinylpyrrolidone)-based copolymers used as stabilizers in aqueous media is reported. Ammonium persulfate or a mixture of ammonium persulfate with CuCl2 or CuBr2 was used as oxidants. The effects of several parameters such as the molar mass and the concentration of the stabilizer as well as the nature of the oxidants on the size, morphology, and the conductivity of the PEDOT particles have been investigated. The distribution of the reactive moieties along the copolymer stabilizer backbone was shown to be crucial to get well-defined PEDOT nano-objects. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3841-3855, 2010