In this paper, two procedures for damage detection in Carbon Fiber-Reinforced Polymer (CFRP) plates are shown. One is based on the use of statistical frequency series to detect the presence of damage. This method was tested experimentally on a CFRP plate with induced damage. The other one is a procedure based on Ritz method and wavelet transform that was applied to the numerical vibration modes of a damaged CFRP plate. The former method can also be used experimentally, even if the ma- terial engineering constants are unknown. Damage detection in composite materials is a very interesting subject in aeronautical engineering, since it permits important maintenance cost reductions and moreover reduces the risk of critical structural failure which might produce fatal consequences in terms of human lives. Clearly it is necessary to develop new techniques to detect damage efficiently. Even if these new techniques cannot locate the damage, they can be used in conjunction with traditional ones for a complete damage characterization. Many of the new damage detection methods are based on vibration test techniques, given the fact that damage modifies the physical characteristics of the material. The nat- ural frequencies and vibration modes therefore change with respect to the undamaged material. The present study is divided into two parts. First, an experimental study of undamaged and damaged clamped plates is performed, and a damage index based on statistical and frequency series is defined. The damage index is an indicator capable of revealing the presence and extent of plate damage. It cannot, however, reveal its position. The piezoelectrics used in the experiments are very thin, and can thus be used as embeded sensors for Structural Health Monitoring (SHM). Second, using the plate vibration modes obtained with a Finite Element Model (FEM), a damage location tech- nique based on the variational Ritz method and wavelet analysis is developed. In this respect, the FEM allows us to simulate different damage types. With the Ritz method, the transversal displacement is approximated by a product series of functions compatible with the boundary conditions, as in the classical work (1).