The anionic polymerization of 2,2,4,4-tetramethyl-6,6-diphenylcyclotrisiloxane (l), its copolymerization with hexamethylcyclotrisiloxane (2), and the homopolymerization of 2 were studied. It was found that the polymerization of 1 initiated with potassium trimethylsilanolate proceeds with the formation of 2,2,4,4,6,6-hexamethyl-8,8-diphenylcyclotetrailoxane (3). When using lithium butyldimethylsilanolate/HMPT as initiator an inversion of the reactivity order in the homopolymerization of 2 and 1 was observed. The results indicate that both propagation and depropagation occur with a high degree of regioselectivity, which is dependent on the applied catalyst.