Proton potential in the medium-strong intramolecular hydrogen bond of acetylacetone is examined on various ab initio and DFT levels. Semiempirical MO methods AM1 and PM3 turn out to be inadequate for the present system. It was shown that the proton donor-proton acceptor distance influences the barrier height while both CO distances introduce the asymmetry to the otherwise symmetric proton potential Ab initio data are fitted to a computationally inexpensive two-state empirical valence bond potential suitable for molecular simulations.