We present a comparative analysis of Cathodoluminescence (CL), Photoluminescence (PL) and Electroluminescence (EL) spectra measured on Si-SiO2 structures with various thicknesses of SiO2 layer. The spectral distributions of the luminescence depend on the technology of the SiO2 layer formation, on its thickness and the type of excitation. The analysis indicates that CL and EL spectra of the Si-SiO2 structures, grown by thermal oxidation of silicon in a “dry” oxygen, are almost identical in spectral composition. The PL of the Si-SiO2 structures provides additional information about the optically active centers in the SiO2 layer. The PL spectra allow tracking changes in the SiO2 layer while increasing its thickness in more detail than the EL and CL. We suggest that there is a substantial difference in the excitation mechanisms of luminescence by electrons (CL and EL) and photons (PL). Therefore, in general case, the luminescence centers identified in PL cannot be directly used for the interpretation of CL and EL spectra. However, analysis of the PL and EL spectra before and after the field degradation of the Si-SiO2 structure as well as analysis of PL spectra of the oxide layers formed by various technologies shows that the model of luminescence centers proposed for red photoluminescence is acceptable for the red luminescence excited by electrons in Si-SiO2 structure.