New hadrons as four-quark states

Starting from the phenomenological evidence of four-quark structures in the scalar meson sector around 1 GeV, we investigate the predictions of a model based on diquark-antidiquark bound states, where the diquarks are assumed to contain also heavy quarks. The predictions are compared with the existing data in the charmonium energy range. A comparison of the tetraquark model with alternative interpretations of the exotic reson-cances is presented.