The problem of actuator/sensor location is examined for the inclusion of piezoelectric smart structural elements in box-type structures. The box is modeled as a system of joined plates in which both extensional and bending deflections are incorporated. A location criterion is developed which is based on the damping injected into the first few modes by a simple constant gain feedback. It is found that the central regions of each face which avoid the edges and corners offer the most promising sites for collocating piezo-actuators and sensors.