Infrared spectra are presented for the main optical properties of poly(methyl methacrylate) films. They are obtained from the complex permittivity using the Drude-Lorentz model for permittivity. This approach is original in obtaining the permittivity and then in obtaining the main optical properties of the polymer film. Classical dispersion analysis of the reflection-absorption spectrum of poly(methyl methacrylate) films cast on the metal mirror was used. Subsequently, the complex electric modulus, energy loss function, optical constants, absorption coefficient, penetration depth, dissipation factor, and complex optical conductivity were obtained from the complex permittivity.