Oxidation of tetrakis(ethylthio)tetrathiafulvalene (TTC2-TTF) with CuCl2 and CuBr2 in acetonitrile yielded the organic radical cation salts, (TTC2-TTF)2[Cu2Cl6] 1 and (TTC2-TTF)(2)[Cu2Br6] 2, whose structures have been determined by X-ray structure analysis. Both 1 and 2 crystallize in the triclinic system, space group P (1) over bar with one molecule per unit cell. 1 : a = 12.065(4), b = 12.644(3), c = 8.988(2) Angstrom, alpha = 103.54(2), beta = 90.24(2), gamma = 112.42(2)degrees. 2 : a = 12.330(3), b = 12.647(2), c = 8.956(2) Angstrom, alpha = 101.72(2), beta = 94.66(2), gamma = 111.69(1)degrees. Both structures consist of two segregated stacks of TTC2-TTF+ donors and Cu(2)X(6)(2-) accepters associated via short S ... X contacts. Consistent with the structural results, the two compounds exhibit low electrical conductivities with sigma 25 degrees C being 4 x 10(-8) and 8 x 10(-8) S cm(-1) for 1 and 2, respectively.