This paper describes a simulation based development process of a control system for a semi-active cabin suspension of an agricultural tractor. During the past ten years cabin suspension has become common in agricultural tractors. At the same time the performance of these suspension systems has also improved a great deal. This trend is mainly due to growing customer needs for better ride comfort, but also partly due to tightening regulations, e.g. directive 2002/44/EC. So far all cabin suspension systems available have been passive. In order to improve the ride comfort further, one possibility is to use semi-active suspension, in which damping, spring rate or both are controlled externally to best fit the prevailing driving situation. MBS (Multi-Body System) simulation has proven to be an efficient tool in suspension system development. For example in tuning the suspension parameters great savings in development time and costs can be achieved by using simulations due to the ideal repeatability and speed of the virtual testing. In this study, combined simulation has been used to develop a control system for a semiactive cabin suspension. The MBS model of the tractor was built up in ADAMS and the control system of the suspension was developed in Matlab/Simulink. With the combined simulation, these two models built up in different software application could be run simultaneously in interaction. The objective for the control system development was to minimize WBV (Whole Body Vibration) exposure and increase the ride comfort of the driver in different virtual test tracks. First, different control methods were roughly tuned and compared. In the second phase, the most promising methods found in the comparison were fine tuned and evaluated. The simulation results with the final parameters show considerable improvement in WBV and ride comfort compared to passive cabin suspension.