Abstract: The optical properties of wood-polyester composites were studied using the measurement of changes in the UV-visible light absorption spectrum. This study aimed to motivate the feasibility of obtaining Wood-Polymer Composites (WPC) displaying a performance superior. Polymer composites exhibited a new UV-visible absorption band at a wavelength (190 nm) which is attributed to interchain interaction. The optical transmission method was successfully used to determine the absorption coefficient (α), the dielectric constant and the energy gap of four samples of wood-polyester composites. The results indicated a significant improvement of the investigated optical properties and showed a strongly dependent on the nature of the material and the radiation type.