The thin layer of poly(3,4-ethylenedioxythiophene) (PEDOT) on the PET film was obtained by a vapor-phase polymerization technique using HAuCl4 as an oxidant. The EDOT monomer was easily oxidized by the HAuCl4 oxidant while HAuCl4 was reduced to form metallic Au nanoparticles. The formation of PEDOT/Au composite film was monitored by UV-vis spectra and SEM, and the formation of metallic Au was confirmed by EDAX and XPS.