Three-dimensional potential energy surfaces for the (X) over tilde (2)A " and (A) over tilde (2)A＇ states of HNF are reported in the present paper. The ab initio calculations are carried out at the multireference configuration interaction (MRD-CI) level of theory employing a large basis set. The (X) over tilde (2)A " potential surface possesses a deep potential well. Both surfaces have a bent equilibrium, at approximately 100 deg for the ground state and at about 125 deg for the excited one. The two electronic states become degenerate at the linear geometry. Variational calculations for the vibrational energies and the corresponding wave functions have been performed on three-dimensional fitted potential energy surfaces. The first 101 levels of the (X) over tilde (2)A " state and the lowest 51 levels of the (A) over tilde (2)A＇ manifold are reported, and their vibrational modes are assigned on the basis of the nodal structure of the corresponding wave functions. The (A) over tilde (2)A＇ vibrational states consist of well-defined polyads with polyad quantum number P = 3v(1) + v(2) + v(3) where v(1) - v(3) are the H-N stretching, bending, and N-F stretching quantum numbers, respectively. The calculated barrier height, vertical and adiabatic excitation energies, as well as the dissociation limits, agree satisfactorily with the available experimental data. This underlines that the overall accuracy of the potential energy surfaces is good.