Scalar Mesons in QCD

We review the analysis of the quark and gluon substructures of the scalar mesons from QCD spectral sum rules and some low-energy theorems applied to the scalar QCD anomaly current. The present data favour equal components of u-baru + d-bard and of gg in the wave functions of the low-mass (below 1 GeV) scalar mesons, which make the wide σ and the narrow f0(980) as η'-like particles having strong couplings to meson pairs through OZI violations. A coherent picture of the other I = 0 scalar mesons spectra within this mixing scheme is shortly discussed. We also expect the a0(980) to be the lowest isovector u-bard state, and the K*0(1430) its d-bars partner