Abstract: This paper is concemed with the dynamic behavior of building structures consisting of multiple tuned mass dampers (MTMD) under harmonic excitation. Comparison is made between MTMD and tuned mass damper (TMD). The structure is modeled as a single degree-of-freedom system. MTMD are joined in parallel and each TMD has the same mass and damping ratio. The natural frequencies of MTMD are assumed to be equally distribued. It is found that the frequency range, the damping ratio and the total number of tuned mass dampers are dominant parmeters of the system for a given mass ratio . Therefore, it is necessary to optimize these parameters. In addition, the optimization of MTMD is found more effective than the optimization of a single TMD in structural vibration control .