The geometry and the vibrational properties of (22×2) missing row reconstructed O/Cu(001) and O/Ag(001) surfaces are investigated by means of density functional theory and density functional perturbation theory, using the local density and the generalized-gradient approximations. Our results predict very similar structural and vibrational properties for the two reconstructed surfaces. In the case of copper our calculations reproduce quite accurately the experimental results, while for the missing row reconstructed O/Ag(001) surface the agreement between theory and experiment is less satisfactory.