A systematic intercomparison between several radiative transfer codes was performed in order to validate the newly developed 3-D spherical harmonics code SHARM-3D. This code is designed for plane-parallel radiance and flux simulations in clear-skies conditions, when the atmosphere is horizontally uniform but surface can be arbitrarily non-homogeneous and anisotropic. For 1-D case, we used widely recognized and well validated codes DISORT and SHDOM, as well as 6S code particularly popular within the land remote sensing community. In 3-D regime, SHARM-3D was compared with SHDOM. Extensive study show that codes SHARM-3D and SHDOM agree to an accuracy of 1-4 percent under the very general conditions.