Current correlators and form factors in the resonance region

Within Resonance Chiral Theory and in the context of QCD current correlators at next-to-leading order in 1/NC, we have analyzed the two-body form factors which include resonances as a final state. The short-distance constraints have been studied. One of the main motivations is the estimation of the chiral low-energy constants at subleading order, that is, keeping full control of the renormalization scale dependence. As an application we show the resonance estimation of some coupling, and .