Accounting for the finite width of the lasing line allows a solution of the lidar equation to be refined. A monostatic aerosol lidar for atmospheric aerosol sensing and a lidar of differential absorption and scattering for sensing of iodine molecules in the atmosphere are considered. The lidar equation for Mie backscattering by aerosol particles has been discussed in detail in (1-3) under assumption that the lasing line is a delta function and does not affect the results of sensing. However, real lasers have the emission spectrum of finite width. In (4) the lidar equation for elastic backscattering by aerosol particles in the atmosphere was proposed taking into account the finite width of the emission line. Krekov et al. (5) performed numerical calculations of the lidar equation for the differential absorption and scattering by gas molecules in the atmosphere using a genetic algorithm. These studies have shown that consideration of the finite width of the laser line will allow the solution of the lidar equation to be refined, especially for the case of very low concentrations of the investigated particles or molecules. The purpose of this work is consideration of the width of the lasing line in a monostatic aerosol lidar intended for sensing of the atmospheric aerosol and in a lidar of differential absorption and scattering intended for sensing of iodine molecules in the atmosphere. First, we will investigate the influence of the lasing line width in the monostatic aerosol lidar intended for atmospheric sensing and will estimate the measurement error of the lidar signal. Let us consider the optical scheme of the lidar shown in Fig. 1. We will characterize the transmission system of this lidar by radiation power P0 transmitted into the atmosphere, laser pulse duration �2 L , and the lasing line will be assumed a Gaussian one with a maximum at the