A topological analysis of the electron density distribution rho(r) in the crystal of 8,9,10,12-tetrafluoro-o-carborane C2B10H8F4 was performed using high-resolution low-temperature (120 K) X-ray diffraction data (14 606 reflections, R = 0.026) and a multipole model for data refinement. Molecules in the crystal (space group Pbcn, Z = 4) occupy special positions on a 2-fold symmetry axis passing through the middle of a C-C bond and the opposite B-B bond of the octahedral cage. Deformation electron density maps as well as maps of the Laplacian of rho(r) showed that electron density is essentially delocalized over the surface of the cage and locally depleted in its center. All B-B and B-C bonds in the polyhedron are characterized by significant bending, which is evident in shifts of their (3,-1) bond critical points from the straight lines between bended atoms. Detailed analysis of rho(r) values and its Laplacian in the bond critical points revealed some unexpected features in the bonding pattern of the structure studied, namely, the positive value of the Laplacian in the homopolar C-C bond and the negative values for the B-C bonds. These data are compared with corresponding ab initio calculations of small deltahedral boranes and carboranes. It is concluded that the electron-withdrawing effect of the fluorine atoms causes considerable redistribution of the electron density in the molecule, and, in particular, this is reflected in the shift of rho(r) from the more electron-rich C-C bonds to the B-C bonds.