The free vibration and damping characteristics of plates consisting of composite stiff-layers and an isotropic viscoelastic core were studied under thermal loads using finite element method. The temperature dependence of viscoelastic core properties and effects of pre-stresses are taken into account. The inherent composite damping and damping due to viscoelastic layer are compared. Parametric study is conducted with fiber angle, ply lay-up, and core thickness as parameters. The results show some interesting phenomenon like shifting of modes with temperature. © 2005 Elsevier Ltd. All rights reserved.