Novel P-containing oxynitrides VZrPON were tested besides their VZrPO oxide precursors in the ammoxidation of 3-picoline and compared with P-free VZrON catalysts for analysing the influence of both incorporated P and N on the catalytic performance. Results of XRD, XPS, P-31 and V-51 MAS NMR as well as of simultaneous in situ-EPR/UV-vis/Raman studies during nitridation have shown that the incorporation of phosphorus enhances the V dispersion, reduces vanadium partially even down to V3+ and leads to the formation of a crystalline ZrV2-xPx,O-7 phase for Zr/V >= 0.5 with V sites surrounded by four O atoms only. N is preferentially incorporated in the vicinity of P, thus, suppressing the formation of V N moieties. These facts may be a reason why the incorporation of P does not markedly improve the catalytic performance of VZrPON catalysts. (C) 2010 Elsevier Inc. All rights reserved.