[en] The anisotropy of impurity absorption in single crystals of CdS:Li was investigated using polarization modulation. A theoretical consideration of dipole absorption in a uniaxial crystal with an allowance for space degeneration of absorbing centres due to the presence of equivalent directions in the crystal lattice was carried out. On the basis of the expressions obtained, the geometry of arrangement of cadmium sulfide of the dipole complexes in the lattice, which contain interstitial lithium, was studied. The model of anisotropic centres is discussed determining the photoconductivity in the ''green'' range of the spectrum of the crystals investigated