Recording of holographic gratings by excitation of long-living metastable electronic states in centrosymmetric sodium nitroprusside can be performed with mutually orthogonal polarized waves. Two different cases have to be distinguished: 1) In a b-cut the optimum diffraction efficiency of 15% is achieved if the mutually orthogonal polarized writing waves form an angle of 45 • with respect to the aand c-axis. This, together with the fact that the polarization state is not changed in the diffraction process, indicates that the gratings originate from the presence of light-induced linear dichroism. 2) For a c-cut the polarization of the diffracted wave turns out to be orthogonal to the one of the incident beam. The efficiency of this so-called anisotropic diffraction reaches a maximum of up to 90% for waves mutually orthogonal polarized along the aand b-axis.