  We study the vector and scalar meson-meson amplitudes up to \sqrt{s}\lesssim
1.4 GeV and their associated spectroscopy. The study has been done considering
jointly the N/D method, Chiral Symmetry and implications from large N_c QCD.
The N/D method provides us with the way to unitarize the tree level amplitudes
constructed in agreement with Chiral Symmetry and its breaking (explicit and
spontaneous). These amplitudes are calculated making use of the lowest order
Chiral Perturbation Theory (\chiPT) Lagrangians and the exchanges of resonances
compatible with Chiral Symmetry as given in. On the other hand the large N_c
considerations allow us to distinguish between elementary (as elementary as the
pions, for instance) and compound (meson-meson) states. Making use of this
formalism one observes that the \sigma, \kappa and a_0(980) resonances are
meson-meson states originating from the unitarization of the lowest order
\chiPT amplitudes. On the other hand, the f_0(980) is a combination of a strong
S-wave meson-meson unitarity effect and of a preexisting singlet resonance with
a mass around 1 GeV.
