Damage detection and identification in civil, mechanical, and aerospace engineering structures by using the dynamic system parameters are widely investigated at present. Damage as a combination of different failure modes in the form of the loss of local stiffness in the structure affects its dynamic characteristics, i.e., the modal frequencies, mode shapes, and modal damping values. The changes in the vibration parameters can be used as indicators in damage detection. According to the process of treating the measured modal parameters, the vibration-based damage identification methods can be classified as model-based and nonmodel-based ones. The model-based methods identify damage by correlating an analysis of structural models, which are usually implemented by the finite element theory, with experimental modal data of the damaged structure. Nonmodel-based damage detection methods are relatively straightforward. The changes in the modal parameters between the intact and damaged states of the structure are directly used to detect and locate the damage in the structure [1-2]. Up to the present, most of the structural damage detection methods are formulated in a one-dimensional space and can be applied only to structures that behave in a beam-like manner or can be decomposed into beam elements. In the present study, the changes in the modal parameters, i.e., natural frequencies, mode shape curvatures, and modal strain energy, are employed to evaluate the possibility of detecting and locating damages in plate-like structures. A finite element investigation on the method of damage detection and localization by using the vibration parameters of the structure is carried out. Since, in actual structures, the damage usually affects the stiffness matrix but not the mass matrix of the system, in the following theoretical development, it is assumed that the damage leads to the loss of stiffness in damaged elements of the system. The change in stiffness due to damage is modeled by the reduction in the elastic modulus of damaged elements. The changes in the modal frequencies, mode shape curvatures, and modal strain energy before and after the introduction of damage are employed to detect the damage presence and location. It is found that the modal parameters are sensitive to damage, and the technique gives a clear identification of its location. 1. Doebling S. W., Farrar C. R., and Prime M. B. A summary review of vibration-based damage identification methods // The Shock and Vibration Digest. – 1998. – Vol. 30 (2), – P. 91 – 105. 2. Zou Y., Tong L., and Steven G. P. Vibration-based model-dependent damage (delamination) identification and health monitoring for composite structures – a review // J. of Sound and Vibration. – 2000, - Vol. 230 (2), – P. 357 – 378.