Poly(methyl methacrylate) doped with CuCl2 was prepared and its electron spin resonance (ESR) spectra and optical properties were studied. The ESR spectra can be accounted for by the presence of two radicals: R-a and R-b. FTIR spectroscopy reveals that there is no main difference of the spectra due to the addition of CuCl2. The structural modifications are identified by investigating the doping level dependence of the peak heights of certain IR absorption peaks. The optical absorption, transmittance, and reflectance measurements were performed for prepared samples. The doping level (W) dependence on the g-factor (g), asymmetry factor (A), peak-to-peak separation (Delta HPP), spin concentration (N), optical energy gap (E-opt), Urbach energy (E-u), refractive index (n), average oscillator wavelength (lambda(o)), and average oscillator strength (S,) were estimated. It was found that these parameters are changed with doping level. These changes suggest high sensitivity of these films to doping that would suggest the applicability in magnetic and/or optical devices. (c) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 108: 1013-1020, 2008.