A semi-active control system of an automotive suspension with an Magneto-Rheological (MR) damper as a key element is considered. Given its hysteretical and nonlinear behavior, the inclusion of a MR damper model in a controller synthesis is presented. Two controllers are proposed from different approaches: LPV control and a Frequency Estimation-Based (FEB) control. The LPV controller uses a LPV model of a quarter of vehicle based on the MR damper dynamics. The FEB controller is a model-free controller. These controllers are compared under comfort oriented standards. Simulation results show these controllers as new alternatives with excellent response for comfort and road holding (improving the comfort between 10-20). %. © 2011 IFAC.