Chalcogenide glasses in the system As_xSe_100-x, as well as As₄₀Se₆₀, and As₅₀Se₅₀ glasses doped with metals (Bi, Ge, Cd, Ag, Sn, Mn, Dy and Sm) were investigated by Raman spectroscopy. The Raman spectra of As_xSe_100-x with 0≤x≤10 suggest that the majority building units are Se chains and Se₈ closed rings. At higher As contents, new structural units are formed from As and Se atoms. The Raman profiles for x>50 are characterized by the presence of strong narrow bands indicating the high ordering in the structure of these glassy materials. The doped samples with small amounts of metals, 0.1 - 1.0 at.%, do not show appreciable changes in their short-range order structure, with the exception of the 0.5 at.% Dy-doped sample. For the sample As₅₀Se₅₀+7.5 at.% Sn, there is direct evidence for the formation of new Sn-based structural units, such as Sn(Se _1/2)₄ tetrahedra.