  The parametric region in the plane defined by the ratios of the energies of
the subsystems and the three body ground state, in which Efimov states can
exist, is determined. We use a renormalizable model that guarantees the general
validity of our results in the context of short range interactions. The
experimental data for one and two-neutron separation energies, implies that
among the halo-nuclei candidates, only C-20 has a possible Efimov state, with
energy less than 14 KeV below the scattering threshold.
