The di-, tri- and tetra-cage coplanar cubanes have been studied at B3LYP/D95** and MP2/D95** levels, and their vibrational frequencies have been calculated at B3LYP/D95** level. All of these species have no imaginary vibrational frequency, so that each of the molecules is a mini- mum at the potential energy hypersurface. Many properties of the molecules, such as geometries, heats of formation and the first ionization potentials, have been studied in this paper. The di-, tri- and tetra-cage coplanar cubanes have been studied at B3LYP / D95 ** and MP2 / D95 ** levels, and their vibrational frequencies have been calculated at B3LYP / D95 ** level. All of these species have no imaginary vibrational frequency, so that each of the molecules is a mini- mum at the potential energy hypersurface. Many properties of the molecules, such as geometries, heats of formation and the first ionization potentials, have been studied in this paper.