Abstract CO—He RF discharge mixtures have been analyzed at various pressures and feed compositions by IR and near UV—VIS emission spectroscopy. The analysis of CO first-overtone emissions has shown the non-Boltzmann character of the ground-state vibrational distributions. The dissociation of CO has been revealed by the presence of various emitting discharge products (CO 2, C 2, O). The effect on the ground vibrational distributions of the various energy exchange processes (e—V, V—V, V—T) has been discussed. CO vibrational distributions in X 1 Σ + and A 1∏ states have also been correlated.