We performed a finite size calculation with lattice size of 15 × 15 × 15a 3 0 based on the model Hamiltonian (17). Numbers of states in the band structure of LaH 3 and LaH 2 are counted as a function of energy. The discrete densities of states were smoothed out by replacing delta peaks with Lorentzian distribution curve of width Γ = 0.3 eV. Our results for LaH 2 and LaH 3 are similar to the previous theoretical calculations by Gupta and Burger [36,38]. In Fig. 15, the pronounced two-peak structure is associated with the flat region of hydrogen bands near symmetry points X, L, K (refer to the band structure Fig. 9 and 10) while the small bump at the zero energy in LaH 2 is associated with the La band near symmetry points W and K. Experiments showed that the small bump shrinks as hydrogen concentration increases and eventually disappears when the sample approaches the trihydride. However Gupta and Burger expected a metallic state for LaH 3 from their LDA calculation which ignored electron correlation. In our calculations, the density of states goes to zero at −2.2 eV, indicating an insulating behavior for LaH 3 . However, the calculated widths for LaH 2 and LaH 3 are considerably smaller than the experiment results, a discrepancy similar to that in the LDA . The experimental **data** also shows a shift of the lowest energy peak when the concentration increases. The positions of calculated peaks do not significantly depend on the concentration and does not agree to the experiment. The origin of these discrepancies is not clear. Since our theory uses some parameters extracted from LDA, similar features except for the band gap may be expected from both theories.