Using the general formalism of structure functions (SF's), the polarization effects in the rare radiative decay of polarized b quarks, b --> s gamma g, are analyzed. Parametrizing the matrix element for the decay b --> s gamma g in terms of weak magnetic moments, which describe the transitions b --> s gamma and b --> sg, we find exact expressions for the SF's which are valid for a wide class of models for the FCNC's. We demonstrated that the different asymmetries in this decay are very sensitive to the model of FCNC's. The numerical calculations (with and without QCD corrections) show that asymmetry in b --> gamma(sg) is large in absolute value and its energy dependence is very sensitive to the choice of model. We also analyze the relative importance of different contributions to the asymmetry in b --> gamma(sg).