The performance of a flowing gas CO//2 laser is analysed and compared with a theoretical model which takes into account the gas flow rate and the CO//2 decomposition. Particular attention has been devoted to the characteristics of slow gas flow as a function of the gas mixture composition. In order to test their model and to optimize the laser performance, the authors analysed the dependence of the output power on the discharge current, gas pressure, flow rate, gas composition and output mirror reflectivity.