The effects of substituent and hybridization of nitrogen atom on hydrogen bonding in the F-H center dot center dot center dot N CX, F-H center dot center dot center dot N(H)=CX, and F-H center dot center dot center dot N(H)(2)-CX complexes have theoretically been studied by MP2 and DFT methods with aug-cc-pVDZ and 6-311++G** basis sets. With respect to the hybridization of nitrogen, sp(3)-hybridized nitrogen forms the strongest bond, followed by sp(2) and then sp. In equilibrium structures, the trend in the two-bond F-19-N-15 spin-spin coupling constants ((2h)J(F-N)) is sp < sp(3) < sp(2). The results of atoms in molecules ( AIM) and natural bond orbital (NBO) analyses are in meaningful relationships with other characteristics of hydrogen bonds, especially with the (2h)J(F-N) values. (C) 2010 Elsevier B.V. All rights reserved.