  We describe the interference between amplitudes $e^+e^- \to \rho \to
\gamma\pi^+\pi^-$ and $e^+e^- \to \phi \to \gamma f_0 \to \gamma\pi^+\pi^-$,
where $f_0$ meson is considered in the frameworks of the four-quark model and
the model of the scalar $K\bar K$ molecule. The general expressions for the
differential cross section with the radiative corrections and two angle cuts
are given. The interference patterns are obtained in the spectrum of the
differential cross section by the energy of the photon and in the full cross
section by the energy of the beams.
