The C15 YMn2 Laves phase compound can absorb hydrogen under moderate pressure up to 4.5 hydrogens per formula unit. In this case, the hydrogen atoms occupy the interstitial Y2Mn2 tetrahedral site. At room temperature these compounds remain cubic C15 and for x >3.5 a rhombohedral distortion occurs. Subjecting YMn2 to a hydrogen pressure of 2 kbars leads to the formation of a novel YMn2H6 hydride with Fm-3m symmetry. Its structural, elastic, magnetic properties are very different from those of well known hydrides YMn2Dx (where x < 4.5). In the YMn2D6 structure, the Mn atoms occupy two different sites: the 8c site with a random substitution of Mn by Y or Mn atoms and the 4a site which is surrounded by 6 H atoms. This new structure is similar to that of the complex metal hydride Mg2FeH6. As the type of bonding is different in the interstitial and complex metal hydride, very different INS spectra should be obtained. Our purpose is to compare the INS spectra of YMn2H6 with that of previous INS spectra of YMn2Hx hydrides to understand this difference.