Two glass systems have been investigated: (100 − x)[12 Al(PO 3) 3 28.5 MgF 2 5 CaF 2 54.5 BaF 2] x V 2O 5 with x = 0, 0.5, 1, 2, 3, 5, 8 and compared with: (100 − x)[12 Al(PO 3) 3 33.5 Mg(PO 3) 2 54.5 Ba(PO 3) 2] x V 2O 5. While the pure phosphate glass system (OV) has a strong reducing action on vanadium, the fluoride-phosphate system (FV) favours higher oxidation states by the lower electron donor properties of fluorine compared with oxygen. As a consequence, in the OV-system V 3+-ions strongly dominate the line shape in the absorption spectra and prevent separation of the optical absorption bands. However, in the FV-system the separation succeeds for the absorption bands of all three valency conditions V 3+, V 4+ and V 5+, which is only possible by the presence of fluorine. The separated absorption bands indicate an orthorhombic symmetry for the V 4+-complexes, which is shifted to a tetragonal symmetry with increasing vanadium oxide and decreasing F/O-ratio. In contrast to an increase of ligand field strength, the ESR-spectra show a decrease of the g-factors within a certain concentration range. This decrease seems to be a result of an exchange of planar-coordinated fluorine by oxygen ligands, combined with a reduction of π-bonding contributions.