Crystalline SbPO 4 and SbOPO 4 have been investigated by using NMR, XPS and IR techniques to understand the changes in the electronic characteristics of phosphorus in PO 4 3 - tetrahedra. The observed values of 3 1 P chemical shift for SbPO 4 and SbOPO 4 , are found to be -18 and -31.8 ppm, respectively, indicating that 3 1 P nuclei are more shielded in SbOPO 4 . The binding energy values for 2p electrons of phosphorus in SbPO 4 and SbOPO 4 are 133.9 and 137.8 eV, respectively, suggesting that the electron density around phosphorus is less for SbOPO 4 . These two apparently contradictory inferences have been explained by considering the decreased paramagnetic contribution to the 3 1 P chemical shift values brought about by the decreased electron density around oxygen atoms present in P-O-Sb 5 + linkages as compared to that of P-O-Sb 3 + linkages. Oxygen 1s XPS and IR studies of these samples provide direct evidence in support of these explanations.