The crystal structure of NH 4 VO 3 was refined by the geometry optimization done by total energy minimization in solid state using DFT/plane waves approach. The lattice parameters were derived by the Le Bail technique from the low temperature X-ray (40-293 K) and synchrotron (100-293 K) powder diffraction data. The structure is formed by the infinite chains of irregular VO 4 tetrahedra running approximately parallel to the caxis, which are interlinked by the ammonium ions placed between them. The ammonium ions link to the [VO 4 ] ∞ chains through one linear, one bifurcated and two trifurcated N-H…O hydrogen bonds. Considering their stability there are six distinct N-H…O hydrogen bonds: two strong with the N-H…O bond angles close to the straight, two medium with the bond angles of 123° and 148° and two very bent (105° and 107°) and hence weak hydrogen bonds. There is a reasonable agreement between the energies of the stretching ν(NH) modes estimated using the optimised N…O contact distances and those obtained experimentally.