The possibility of using CO2 lasers, with different lasing line widths for gas analysis of the atmosphere by the differential absorption method has been investigated. A technique for determining the concentration of gaseous components of the atmosphere has been proposed in the case of single-frequency sounding. The calculated effective absorption coefficients of some gases in the spectral regions of the first and second harmonics of the CO2 laser are presented. It is shown that the CO2 lasers with different lasing line widths made feasible the determination of the background values of concentration of carbon dioxide, ammonia, and water vapor in the case of single-frequency sounding. In the region of the second harmonic of the CO2 laser, the proposed technique can be used to eliminate the interfering effect of the water vapor absorption in sounding of OCS and NO and to detect simultaneously the background values of concentration of carbon monoxide and water vapor in the case of sounding at the second harmonic of the lasing line of the CO2 laser 9R18 with different spectral widths.