  We discuss the Pad\'e approximation to the $\pi\pi$ scattering amplitudes in
1--loop chiral perturbation theory. The approximation restores unitarity and
can reproduce the correct resonance poles, but the approximation violates
crossing symmetry and produce spurious poles on the complex $s$ plane and
therefore plagues its predictions on physical quantities at quantitative level.
However we find that one virtual state in the IJ=20 channel may have physical
relevance.
