A simple algorithm is derived to retrieve the aerosol backscattering and extinction vertical profiles from simultaneously detected ground and space elastic lidar signals, without any a priori hypothesis on aerosol particles properties. This technique can be applied at any wavelength whenever two "counter looking" lidars are available and the atmosphere can be considered horizontally homogeneous in a spatial scale of the order of the distance between the two lidar beams. To test the accuracy of the algorithm a numerical simulation has been performed. Moreover, it has been applied in a real case to level 1 products from CALIPSO.