The hydrogen-bonding (H-bonding) interactions in alpha-helical and beta-sheet model peptides have been studied by using the atoms-in-molecule (AIM) approach. The relative importance of NH center dot center dot center dot O and CH center dot center dot center dot O H-bonding interactions in the different secondary elements such as alpha-helix, parallel, and antiparallel beta-sheets have been assessed. The electron density values at the NH center dot center dot center dot O bond are higher than those of the CH center dot center dot center dot O bonds in the alpha-helical conformation. The electron density values at the H-bonded critical points (HBCPs) corresponding to NH center dot center dot center dot O and CH center dot center dot center dot O interactions are nearly equal in the parallel beta-sheet of the order of 10(-3) au, whereas in the case of antiparallel beta-sheets, rho(r(c)) values for NH center dot center dot center dot O and CH center dot center dot center dot O interactions are of the order of 10(-2) and 10(-3) au, respectively. It is interesting to point out here that the weakening of NH center dot center dot center dot O interactions in the parallel beta-sheet arrangement is evident from the AIM analysis. This is concomitant with the increase in the NH center dot center dot center dot O distance in the parallel beta-sheet conformation. In addition to the clear description of H-bonding by electron density at the HBCP, possible good linear relationships between the electron density at ring critical points (RCP) and stabilization energy (SE) have been observed corresponding to the various beta-sheet conformations.