This paper is concerned with the investigation of the closed-loop structure of an H ∞ control system. It is shown that H ∞ controller is represented, like Linear Quadratic Gaussian control, as a pseudo state feedback, that is, a state feedback interconnected with an observer. However, in the H ∞ control problem (in particular, discrete-time cases) the control structure is more complicated since we cannot choose the state feedback and the observer independently.