Abstract The reactivities and bonding characteristics of carbon and nitrogen hydride species, CH x ( x=1–4) and NH y ( y=1–3), on wurtzite AlN(0001) surface have been investigated using ab initio molecular orbital calculations performed at HF/6-31G(d) level of theory in order to suggest a substrate pretreatment for chemical vapor deposition of diamond films on AlN substrate. It is shown that the ionic carbon and nitrogen hydride species possess higher chemical reactivity with AlN substrate than the corresponding neutral species. Both the carbon and nitrogen hydrides, especially for the nitrogen hydrides, prefer bonding to the top site of the aluminum atom to the three-fold hollow site above the nitrogen atom on the 〈0001〉 direction of w-AlN. NH 2 species is found to form the most stable interfacial bond with the Al atom on the surface with a binding energy approximately 20 kcal mol −1 more than that of CH 3. Our results imply that a surface pretreatment of AlN substrate with NH 2 species before the diamond deposition would facilitate stable interfacial bonding and hence a good adhesion of the grown film with the substrate.