We have monitored with Raman spectroscopy the metal insulator transition of Y films grown on (1 1 1) CaF 2 substrates and capped with Pd. Characteristic for the γ phase is a Raman spectrum with nine lines at room temperature. In the stoichiometric β phase, YH 2 shows only one line. In the superstoichiometric β phase of YH 2+δ we find changes in the spectra which are not compatible with a cubic lattice. The Raman mapping image during unloading of a Y film shows a regime of coexistence between the γ and the superstoichiometric β phase. The results are compared with measurements on Mg 0.1 Y 0.9 H x which also show a distortion of the cubic lattice.