This paper is concerned with the analysis of active and passive hybrid actions in structures with active constrained damping layers (ACL). A system model is derived via Hamilton’s Principle, based on the constitutive equations of the elastic, viscoelastic, and piezoelectric materials. The model converges to a fully-active piezotronic system as the thickness of the viscoelastic material (VEM) layer approaches zero. A mixed Galerkin-GHM method is employed to discretize and analyze the model in time domain. With an LQR optimal control formulation, the effects of the active constrained layer configuration on the system vibration suppression performance and control effort requirements are investigated. Analysis illustrate that the active piezoelectric action with proper feedback controls will always enhance the damping ability of the passive constrained layer. On the other hand, the viscoelastic layer will reduce the direct control authorities from the active source to the host structure. The significance of this effect depends very much on the viscoelastic layer thickness and material properties. Therefore, with some parameter combinations, the ACL configuration could require more control effort while achieving less vibration reductions compared to a fully-active system. Through analyzing the performance and control effort indices, the conditions where this active-passive hybrid approach can outperform both the passive and active systems are quantified. Based on this study, design guidelines can be set up to effectively integrate the host structure with the piezoelectric and viscoelastic materials, such that a true active-passive hybrid control system can be achieved.