Many properties of chalcogenide amorphous semiconductors, such as electric conductivity, optical constants etc. depend on the type of the structural unit in the amorphous structure i.e. distribution of the nearest neighbor atoms. Obviously the identification of the type of the structural units is of great importance. Cu-25 [AsSe1.4I0.2](75) amorphous system and its crystalline phase prepared by slow cooling of the melt were analyzed on automatic X-ray diffractometer equipment. Using X-ray diffraction data we obtained the structure factor (SF). The reduced radial distribution function (RDF) was obtained in two ways: using standard method, Fourier transformation of SF, and maximum-entropy method. RDF analysis results are in agreement with model calculation, which proves the domination of tetrahedral structural units.