The IR and the Raman spectra of the Ca₃Sc₂Ge₃O₁₂ (CaSGG) garnet crystal have been measured and discussed in terms of internal and external modes of the tetrahedral GeO^4-₄ moiety. Some important aspects of the electronic spectroscopy of these materials activated with luminescent ions, i.e. the multiphonon relaxation of the excited states and the vibrational structure of the optical bands, have been taken into consideration, and correspondences with the vibrational properties of the host lattice have been presented.