The state-of-the-art of theoretical-computational modelling of infrared (IR) spectra in peptides and proteins is able to reproduce the main spectral features involved in the secondary-structure organisation. The results so far collected, clearly show that the complexity of the atomic processes inherent to the IR spectra makes the often used empirical secondary-structure/frequency correlations inaccurate and possibly misleading. The use of extended configurational sampling as provided by, for example, molecular dynamics simulations and of a physically coherent treatment of both the quantum degrees of freedom and their coupling with the semiclassical atomic motions, promises to open the way to interpret and predict IR temperature-dependent and time-dependent spectral signals, in particular for the study of folding/unfolding transitions.