The structure of the (66-x)ZnO-xNa(2)O-33.4P(2)O(5) composition line, selected for the development of low-Tg and stable glasses, has been investigated by 1D/2D NMR spectroscopy. If standard 1D P-31 MAS-NMR experiments give access to the Q(n) speciation and show the presence of Q(0), Q(1) and Q(2) sites within the glass structure, application of the homonuclear through-space correlation technique (P-31 DQ-SQ) allows for a more accurate description of the phosphate units. Clear distinction between the Q(1) sites involved in dimmers or in longer chains has been derived from 2D NMR correlation maps and leads to the reassignment of Q(1) into Q(1,1) and Q(1,2) species. Na-23 and Na-23(P-31) REDOR MAS-NMR experiments have been used to analyse the Na+ ions distribution and its interaction with the phosphate network. Zn-67 static NMR experiments, performed at very high field, were carried out and suggest a constant Zn2+ coordination state all along the composition line. The results have been used to discuss the impact of the Zn2+/Na+ ratio on the extent of disorder within the glass network expressed in terms of Qn dismutation equilibrium constant and phosphate chain length distribution. (C) 2015 Elsevier B.V. All rights reserved.