Ab initio molecular orbital calculations have been performed in the study of the hydrogen-bonded complexes between hydrogen peroxide and hydrogen halide (XH, X = F, Cl). Five stationary points are characterized (structures 1-5); using different basis sets (6-31G** and 6-311G(3d,2p)), with and without adding diffuse functions, and employing different levels of theory (HF, MP2, MP4(SDTQ)). The nature of the studied structures has been analyzed; structures 1, 3, and 5 are true minima, and structures 2, and 4 are transition states. The binding energies of these complexes have been determined and corrected for the basis set superposition error (BSSE).