The optical properties of LuNi5 − xCux intermetallic compounds (x = 0, 1, 2) have been investigated using ellipsometry in the wavelength range of 0.22–15 μm. It has been established that the partial substitution of nickel by copper leads to substantial variations in the spectral characteristics, as well as in the plasma and relaxation frequencies of conduction electrons. Self-consistent calculations of the electronic structure of these compounds have been performed in the approximation of the local electron spin density. The experimental frequency dependences of the optical conductivity in the interband optical absorption region have been interpreted based on the calculated densities of electron states.