The aim of this paper is to investigate the feasibility of using clay suspensions in dynamic dense medium separation of post-consumer plastics. The Theological behavior of suspensions formed with different commercial clay samples was studied to ascertain that both viscosity and stability could be maintained in the range required by dense medium separation systems. Suspensions made with a selected clay sample were used in a laboratory test rig equipped with a conical cyclone and a cylindrical cyclone with peripheral underflow discharge. Preliminary separation tests were carried out using different density plastic tracers. The results with both separators demonstrated that the separation of two plastics of different densities can be obtained.