This study presents the plasma diagnostics of a glow discharge produced in two different mixtures, CO 2 /He and CO 2 /Ar, at a constant pressure of 1.5 Torr. The experiment was conducted to determine the carbon dioxide decomposition in the plasma by using the optical emission spectroscopy ( OES ) method through identifying lines and emission bands in the spectra. In addition, an electrical characterization of the mixture plasma was made by the determination of ion density ( n i ) and the electronic temperature ( T e ) , estimated through a double Langmuir probe. The electronic temperature for the mixture plasma was in the range of 2.07-5.37 eV, and the ion density between 2 . 15 × 10 9 and 18 . 70 × 10 9 particles/cm 3 . The principal bands and lines identified in the OES correspond to CO + 2 , CO 2 , CO + , CO, O*, O 2 , O + 2 , C 2 , He* and Ar*.