This chapter addresses the central issue of the disturbance attenuation and decoupling. Two types of FAS models are introduced, one is subject to deterministic disturbances, and the other is subject to dynamical disturbances. The problem of disturbance attenuation via state feedback for the type of FASs with deterministic disturbances is firstly dealt with. A parametric solution is provided, which allows us to optimize the design parameters F and Z to improve certain performance of the designed system. The problem of asymptotic disturbance decoupling via output feedback for the type of FASs with dynamical disturbances is then handled. Again, a parametric solution is proposed, with which additional performance requirements of the closed-loop system can be insured by optimizing the design DOFs. Finally, a coarse-fine tracking system is treated as an illustrative example to demonstrate the effect of the proposed approach.