For spacecraft with large flexible antennas, and/or flexible support structures, suppressing vibrations caused by on-orbit operational disturbances (e.g., antenna slew manoeuvres and thruster firings) is a challenging problem. In the past several years, advances in smart structure technologies have made their use in real-time dynamic control of a structure possible. This paper discusses analytical investigations that are focused on the development of improved vibration suppression techniques for flexible spacecraft structures using smart structure actuators and sensors. In general, active control of large flexible structures can be used to improve performance, e.g., shape fidelity, line-of-sight pointing accuracy, and vibration and disturbance suppression. Large-scale models of such structures (e.g., finite element models) are appropriate for dynamic simulation but cannot be used as a basis for control algorithms, which must be implemented via computer in real-time. Therefore, control algorithms are often based on Reduced-Order Models (ROM) of the structure dynamics. Whenever such a controller operates in closed-loop with the actual structure, unwanted controller-structure interaction (CSI) occurs due to un-modeled dynamics. CSI can cause performance degradation and even instability. These instabilities can easily be relieved by the use of low-order residual mode filters (RMF). These filters can be added on after the original ROM controller has been designed, and they produce very little degradation of designed performance while yielding an acceptable stability margin for closed-loop operation. The research presented in this paper integrates smart structure control technologies with the ROM-RMF control technique for active vibration control of a flexible spacecraft structure.