Poly(3,4-ethylenedioxythiophene) nanoparticles with narrow size distribution were prepared in organic dispersant media in the presence of both iron(III) dodecylbenzenesulfonate {Fe(DBS)(3)}acting as both an oxidant and a stabilizerand -functionalized polyisoprenes (omega-R-PI) as costabilizers. The effects of the solvent nature and concentration of Fe(DBS)(3) on the size and morphology of the PEDOT particles were first studied in the absence of costabilizer. Second, the effects of the molar mass, concentration, and nature of the functional end group of the polyisoprene costabilizer were investigated. PEDOT nano-objects were characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), dynamic light scattering (DLS), and conductivity measurements.