Using a combination of high resolution X-ray powder diffraction and X-ray Raman scattering spectroscopyat the B K- and Ca L$_{2,3}$-edges, we analyzed the reaction products of Ca(BH$_{4}$)$_{2}$ after annealing at 350 $∘$C and 400 $∘$Cunder vacuum conditions. We observed the formation of nanocrystalline/amorphous CaB$_6$ mainly and found only small contributions from amorphous B for annealing times larger than 2 h. For short annealing times of 0.5 h at 400 $∘$C we observed neither Ca(BH$_{4}$)$_{2}$nor CaB$_6$. The results indicate a reaction pathway in which Ca(BH$_{4}$)$_{2}$ decomposes to B and CaH$_2$ and finally reacts to form CaB$_6$.These findings confirm the potential of using Ca(BH$_{4}$)$_{2}$ as a hydrogen storage medium and imply the desiredcycling capabilities for achieving high-density hydrogen storage materials.