Tin-antimony-selenium (Sn-Sb-Se)-based systems belong to the ternary chalcogenide compounds of IV-V-VI group. They have potential applications in infrared region due to their heavy elemental masses, continuous variation of band gap-energies and lattice constants as well as electrical properties, with compositions. Structures of melt quench-synthesized samples of Snx-Sb5-Se95-x system, where x = 0, 5, 10 and 12.5-mole have been studied using Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. FTIR spectra illustrates that addition of Sn-mole to the system causes a shift in IR-peak's intensity and width from long to the short wavelength. This change implies the breaking of Se chains that appeared around 210-254 cm-1 and the occurrence of pyramidal SbSe3 around 147-210 cm-1 and asymmetrical tetrahedral SnSe4 mode around 117-145 cm-1 for Sn = 5 mole up to 180 cm-1 in Sn = 12.5 mole spectra. Raman spectra show that a pyramidal SbSe3 peak is cited at 190-cm-1. The intensity of this peak is shifted towards -183 cm-1 when Sn-mole is added to the system. The results confirm the validity of using 4, 3 and 2 as co-ordination numbers of Sn, Sb and Se, respectively, in the amorphous region, which is contained by the average co-ordination number, μ � 2.4 and the fraction of Sn-Se bonds, fSn-Se < 44.3. © 2009 King Saud University.