Structural bonds, particularly the ones made of composite materials, have many advantages over other assembly methods. The progress in mastering these two complementary technologies (i.e. structural bonding and composite materials), has made it possible to consider their use in many industrial fields including aeronautics and automobile. Many references exist on bonding quality assessment, but none was addressing the identification of degraded adhesive interface. This work presents numerical and experimental results on the evaluation of the quality of bonding in a metal/adhesive/carbon-epoxy composite structure using Lamb guided waves. For two studied samples, only one of the two interfaces has its bonding quality degraded by inserting a release agent while keeping a good adhesion for the other interface (adhesive degradation). For one other sample, the cross-linking of the epoxy adhesive is partial (cohesive degradation). A numerical study, based on the semi-analytical finite element method (SAFE), is performed. The SAFE model uses extremely thin elastic layers, called interphases, between the adhesive and the plates, which enable an investigation of the bonding quality. Various samples with very different adhesion levels, indicated by a parameter related to the interphase, are investigated and a data base of dispersion curves is thus obtained. An experimental study, based on generation of waves by a piezocomposite transducer and reception by a laser vibrometer, is then performed to plot the experimental dispersion curves. On each experimental result, numerically computed Lamb dispersion curves are superimposed, and the most adequate value of the adhesion quality parameter for each interphase is determined. The different samples quality can be thus identified. Moreover, it is possible to identify on which interface (metal/adhesive or composite/adhesive interface) the quality of the adhesion is degraded.