Poly(o-methoxyaniline) was prepared by the chemical oxidation of the monomer with ammonium peroxydisulfate in the presence of the following acids : hydrochloric, p-toluenesulfonic, dodecylbenzenosulfonic and dodecylsulfuric. The polymers obtained are soluble in dimethylformamide and this enabled the preparation of films by casting. The electrochemical behavior of the polymers prepared by chemical synthesis is very similar to polyaniline prepared by electrochemical methods. Impedance spectroscopy measurements indicated that the acid affects mainly the potential range where the charge transfer resistance is lower. The diffusion coefficients obtained by impedance spectroscopy are higher for poly(o-methoxyaniline) doped with chloridric and p-toluene sulfonic acids than for those doped with dodecylbenzenosulfonic and dodecylsulfuric acids.