Abstract. We show that all possible categories of Yetter-Drinfeld modules over a quasi-Hopf algebra H are isomorphic. We prove also that the category H H YD fd of finite dimensional left Yetter-Drinfeld modules is rigid and then we compute explicitly the canonical isomorphisms in H H YD fd . Finally, we show that certain duals of H 0 , the braided Hopf algebra introduced in [6,7], are isomorphic as braided Hopf algebras if H is a finite dimensional triangular quasi-Hopf algebra.