Ab initio calculations were performed at the MP2/6-311++G(2d,2p) level of theory to obtain optimized geometries, dipole moments, binding energies and harmonic vibrational frequencies for the symmetrical T-shaped structures of XH⋯π bonded complexes involving ethylene (as the proton-acceptor) and the hydrogen halide molecules HF, HCl and HBr (as the proton donors). The relative stabilities of the D-containing isotopomers C 2H 4⋯DX and C 2H 2HD⋯HX were also determined from their zero-point energies. It was found that the D-bonded isotopomer (C 2H 4⋯DX) was more thermodynamically stable than the H-bonded isotopomer (C 2H 2HD⋯HX) for HF, HCl and HBr-containing complexes, previous studies on the weakly bound T-shaped complexes C 2H 2⋯HX also found that the D-bonded species was more stable than the H-bonded species.