The study of the CO–N2 laser described in a preceding paper is pursued here by electronic spectroscopy. It is shown that the emission intensity of the red and violet systems of the CN radical present in the laser tube is related to the infrared laser action. Investigation of this effect leads to the conclusion that, after its formation, CN is electronically excited by collision, with vibrationally excited nitrogen molecules. The effect on the laser and CN emissions of a small addition of gases such as O2, NO, and CO2 is studied and discussed. All the observed facts are interpreted by a theory based only on the presence of N(4S) atoms and vibrationally excited molecules N2(X1Σg+).