A single crystal of phase 1 of 1,2-difluoroethane was grown from the melt directly on an X-ray diffractometer close to the melting point of 169 K. It crystallizes in the monoclinic space group C2/c with lattice parameters a = 7.775(4), b = 4.4973(7), c = 9.024(3) Å, β = 101.73(1)°, V = 308.9(2) Å3, d calc = 1.420 g cm−3 for Z = 4. A second phase of 1,2-difluoroethane was obtained under similar conditions which crystallizes in the orthorhombic space group P212121 with the unit cell parameters a = 8.0467(16), b = 4.5086(9), c = 8.279(2) Å,V = 300.36(11) Å3, d calc = 1.461 g cm−3 for Z = 4. In both phases the 1,2-difluoroethane molecules adopt the gauche conformation with F–C–C–F torsion angles close to 68°. Crystals of 1,2-diiodoethane C2H4I2 were grown from pentane at −30°C. A platelet single crystal of the size 0.35 × 0.25 × 0.03 mm was measured with Mo Kα-radiation at 153 K. 1,2-Diiodoethane crystallizes in the monoclinic space group P21/n with a unit cell of a = 4.6051(7), b = 12.939(2), c = 4.7318(7) Å, β = 104.636(3)°, V = 272.79(7) Å3, Z = 2, d calc = 3.431 g cm−3, μ(MoKα) = 11.353 mm−1. In the molecule the two neighboring iodine atoms are positioned anti. The shortest intermolecular contacts occur via iodine–iodine interactions resulting in layers of molecules in the crystal.