Based on well founded criteria for selecting absorption lines and a proposed algorithm for calculating the transmission of the atmosphere, a technique is developed to search for informative wavelengths for gas analysis by differential absorption lidar (DIAL). This technique can be used in any spectral range provided data on the laser sources are provided. The results of a search for informative probe wavelengths in the mid-IR range are presented. The feasibility of using an overtone CO laser for lidar probing of trace gases in the atmosphere is evaluated. These calculations confirm the prospects for the use of overtone CO lasers for remote gas analysis of the atmosphere.