Heavy-meson decays are important sources of information about scalar resonances. Hopefully, they may also shed light into meson-meson scattering amplitudes. In a recent work, our group has studied the low-energy sector of the reaction D+ → K- p+ p+ by means of chiral SU(3)×SU(3) effective lagrangians, which include scalar resonances and allow a consistent treatment of the primary weak vertex. In the framework of the quasi two-body approximation, the decay amplitude involves a non-resonant background superimposed to processes in which the outgoing mesons interact before reaching the detector. As p+p+ scattering can be safely neglected in this problem, final state interactions involve just the elastic K p amplitude. We discuss whether and how information about K p scattering at low energies can be extracted from D+ decays.