Our aim in this talk is to discuss the existence of finite dimensional attractors for nonautonomous dissipative systems.Two approaches have been proposed in order to extend the notion of a global attractor to nonautonomous systems,namely,a uniform attractor and a pullback attractor.Unfortunately,these two approaches present essential drawbacks,namely,an artificial infinite dimensionality for uniform attractors and the question of the forward convergence for pullback attractors.We show that the notion of an exponential attractor allows to overcome the problem of the forward attraction and yields a satisfactory finite dimensional reduction for nonautonomous dissipative systems.