The compound bis(di-mu-ethoxo-bis(3,5-di-tert-butylsemiquinonato)dicopper(II)) has been synthesized and its structure was determined by single-crystal X-ray diffraction. The compound crystallizes in the monoclinic system, space group C-2/c, with a = 37.736(8) Angstrom, b = 9.173(2) Angstrom, c = 23.270(5) Angstrom, beta = 122.24(3)degrees. The structure can be described as a Lewis adduct between two dinuclear [Cu(DBSQ)(C2H5O)](2) units (DBSQ = 3,54-tert-butyl-semiquinonato). The temperature dependence of the magnetic susceptibility was efficiently analyzed by a combined DFT/experimental approach, showing that a rather strong ferromagnetic interaction exists between the DBSQ(-) and the copper(II) ions modulated by an antiferromagnetic interaction between the two copper(II) ions of the dinuclear units. Weak antiferromagnetism between the two units in the unit cell was measured.