This work suggests a possible phenomenon of the blue-shifted hydrogen bond, which is due to the compression caused by two opposite type of interactions in X-H center dot center dot center dot Y system (Benzene center dot center dot center dot H-F and T-shaped benzene dimer have been considered as model systems). One type is the attraction between H-bond acceptor and remote part of H-bond donor and the other type is the repulsion between X-H and H-bond acceptor. The results obtained from molecular orbital interactions reveal that the repulsive four-electron-two-orbital interactions between the ax-H orbitals of H-bond donor and the occupied orbitals of H-bond acceptor play an important role towards characterization of blue-shifted hydrogen bond with shortening of the X-H bond. (c) 2005 Elsevier B.V. All rights reserved.