Recent development of the X-ray analysis of electron densities has made it possible to get atomic orbitals with the least-squares method incorporating orthonormal relationships between atomic orbitals. It has been applied to several transition metal complexes. The method can also be applied to the X-ray analysis of molecular orbitals. In this analysis the scattering from the two-center electrons play an important role. Their contribution to structure factors of diformohydrazide is calculated and are shown to be significant enough for molecular orbitals to be determined by the analysis. Several other problems concerning with the X-ray analysis of molecular orbitals are also discussed.