First-principle calculations based on density functional theory were used to investigate the stability and the shape of ZnF2 crystals in vacuum. We present and discuss the results of calculations of the ZnF2 bulk and surface structure, in the rutile and CaCl2 modifications. According to our bulk calculations, the rutile and the CaCl2 structures have similar lattice parameters and bulk energy. The surface energies calculated for the two structures show some differences, but the relative stability of the surfaces stays the same for both structures.