The lidar equation for the Raman back scattering by benzene and toluene molecules computer simulation in the ranging distance from 0.1 up to 5 km at the YAG-Nd laser radiation wavelengths of 532, 355 and 266 nm has been fulfilled. It has been established that the optimal for the signal to noise ratio criteria and Raman power maximal value recording in such a lidar system is the laser radiation wavelength of 266 nm at the distance up to 1.7 km.