A structural classification of dimers, containing the Cu(μ-Cl)2Cu core, based on data obtained from X-ray diffraction analysis reported in the literature has been performed. In these complexes, the local geometry around the copper metal center is generally a square pyramid, with a different degree of distortion towards a trigonal bipyramid. The global geometry of the dinuclear complex can be described in terms of the relative arrangement of the two square pyramids, giving rise to three types of geometries, termed: coplanar bases, parallel bases and perpendicular bases. Ideal models representing these geometries were defined and EH calculations were performed in each case, showing the different molecular orbitals involved in their corresponding frontier orbitals, together with their energy. EH calculations were also carried out for dimers embodying different type of structural distortions from the ideal models. The results obtained from those EH calculations have proven to be extremely useful for the proper interpretation and correlation of the magnetic data and dimer structure for those Cu(μ-Cl)2Cu complexes reported in the literature.