Features of the optical properties of nanostructured samples of cupric oxide CuO prepared by shock wave loading (SWL) and by high pressure torsion (HPT) methods have been investigated by means of spectroscopic ellipsometry in the range of 0.5-5.0 eV. The results for nanostructured samples are discussed in comparison with the measurement data of the CuO single crystal. Dispersion of the components of the complex permittivity in nanostructured CuO samples is significantly different from that for the single crystal. The optical spectral density of the nanostructured CuO is redistributed from the energy region above the fundamental absorption edge to the region below the edge. The shift is unexpected strong for samples prepared by the HPT method. The intensity of the optical spectra is suppressed in the range above the fundamental absorption edge and increases in low-energy one. It has been shown that the energy positions of the main electronic transitions in nanostructured samples on the whole are the same as in the single crystal; at the same time, intensity of the low-energy transitions increases. The possible causes of this increase and resolution of the fine absorption structure of the nanostructured CuO are discussed.