Vibration control has always been a challenging problem to the helicopter designer. This paper addresses the problem of the formulation and solution of an active vibration control scheme for helicopters, based on the concept of active control of structural response. First, using a mathematical procedure employing the Fisher information matrix, optimum sensor locations have been identified in a three-dimensional model of a flexible fuselage structure. The reference parameters used in the selection process are the elements of a vector defined as the effective independence distribution vector and the condition number of the Fisher information matrix. It is observed that, irrespective of the excitation frequency, these optimally selected sensor locations experience relatively high levels of vibration. Then, using the measurement from these optimal sensor locations, a multi-input/multi-output control problem has been formulated and solved to obtain the active control forces required for vibration minimization in the helicopter fuselage. It is observed that sensor locations have a significant influence on the level of vibration reduction in a fuselage structure.