Lidar (Light radar) is a suitable tool for studying of the chemical and physical state of the atmosphere. Nowadays, LIDAR represents a broad class of sophisticated, and often, very expensive techniques. Still, the most common is, so called, classic lidar (backscattering lidar). The equation for the classic lidar contains, however, two variables. A certain relation between these variables is usually suggested (to reduce this number to one) but such an approach can't be accepted in a general case (heterogeneous aerosol, for example). During the seminar, a novel procedure for retrieving both of these variables from lidar data will be presented. The procedure allows one to derive a vertical profile of both variables (extinction and backscattering coefficients of the atmosphere) without any assumption being made. This is worth of noting because without knowing of both of these profiles the interpretation of observed changes is strongly limited. The procedure is tested with simulated and real (lidar in Thaloniki, Greece) lidar measurements.