Relevance of final state interactions in eta'->eta pi pi decays

A study of the eta'->eta pi pi Dalitz plot distribution is presented in this talk. The size of the branching ratio is properly understood within U(3) Chiral Perturbation Theory and Resonance Chiral Theory, in the framework of the 1/Nc expansion. Nonetheless, unitarity effects of pion loops must be incorporated in order to achieve an appropriate description of the Dalitz slope parameters. After taking the final state interactions into account, our predictions become now in agreement with the available experimental measurements, although some clear differences show up with respect to previous theoretical estimates.