A structural investigation of (100-y)[50P2O5-15ZnO-(35−x)PbO-xCdO]-yAl2O3 polyphosphate glasses was carried out using Raman, NMR (31P, 207Pb and 27Al) and XPS spectroscopies. In alumina-free glasses (y=0), the CdO substitution for PbO induces a strengthening of the network formation, up to x=20. For x>20, the network connectivity decreases because less cations are located in network former sites. In aluminophosphate glasses (x=20 and 0<y≤8) the determination of oxygen sites distribution, evaluated from the 31P NMR data, agrees with the O1s XPS results and reveals the formation of Al–O–Al bonds. Thecompositional dependence of glass structure and properties is qualitatively understood using structuralinvestigations and site distribution. The partial dissolution of alumina in the glass results from the strongnetwork connectivity of the basic compositional glass (x=20). For the 0≤y<4 compositional range, the Al3+cations are mainly incorporated in six-fold coordination, and have a limited effect on the glass network. On the contrary for x≥4, a conjugated effect of the multiplicity of the Al coordination number (4, 5 and 6)together with the Al–O–Al bridges contributes increasingly to the compactness and the connectivity of thepolyphosphate network. This leads to a large improvement of properties, such as a higher resistance towater corrosion (6×10−10 g cm−2 min−1 at 22°C)< Leer menos