The structures of the ordered diamond(100)-2x1-2NH(2), disordered diamond(110)-1x1-2NH(2), and quasiordered diamond(111)-1x1-NH2 surfaces were calculated using molecular mechanics and density functional approaches. The surface infrared spectra were simulated using force field molecular dynamics and compared to experimental observations. Hydrogen bonding was found to play a significant role in the structures and spectroscopic properties of these surfaces.