The application of control techniques to offshore wind turbines has the potential to significantly improve the structural response of these systems. A new simulation tool is developed that can be utilized to model passive, semi-active and active structural control systems in wind turbines. Two independent, single degree of freedom (DOF) tuned mass- damper (TMD) devices are incorporated into a modified version of the aero-elastic code FAST (Fatigue, Aerodynamics, Structures and Turbulence). The TMDs are located in the nacelle of the turbine model, with one TMD translating in the fore-aft direction, and the other in the side-side direction. The equations of motion of the TMDs are incorporated into the source code of FAST, yielding a more realistic system for modeling structural control in wind turbines than has previously been modeled. The stiffness, damping and commanded force of each TMD are controllable through the FAST-Simulink interface, and so idealizations of semi-active and active control approaches can be implemented. A parametric study is performed to determine the optimal parameters of a passive single DOF, fore-aft, TMD system in both a barge-type and monopile support structure. The wind turbine models equipped with TMDs are then simulated and the performance of these new systems is evaluated. The results indicate that passive control approaches can be used to improve the structural response of offshore wind turbines. The results also demonstrate the potential for active control approaches. Copyright © 2010 John Wiley & Sons, Ltd.