  Pion-pion scattering amplitude obtained from one-loop Chiral Perturbation
Theory (ChPT) is crossing symmetric, however the corresponding partial-wave
amplitudes do not respect exact unitarity relation. There are different
approaches to get unitarized results from ChPT. Here we consider the inverse
amplitude method (IAM) and, using the Roskies relations, we measure the amount
of crossing symmetry violation when IAM is used in order to fit pion-pion
phase-shifts to experimental data in the resonance region. We also show the
unitarity violation of the crossing symmetric ChPT amplitude with its
parameters fixed in order to fit to experimental phase-shifts.
