A theory of sandwich plates with composite-material facings and piezoelectric actuators-stiffeners bonded to the surface or embedded in the facings is developed. The stiffeners bonded to the surfaces are modeled using either the plane stress assumption or a first-order shear deformable theory. The former approach is appropriate if the stiffeners represent thin strips while the latter method can be used in the case where the stiffeners are relatively deep piezoelectric ribs. The stiffeners embedded in the facings in the form of piezoelectric strips are considered using the plane stress assumption.