So far, spectroscopy is one of the fundamental fields involved in the study of non-perturbative QCD. Although some meson multiplets are well known, many others are not completed yet or need to be furthermore investigated. Many new resonances need still interpretation: probably many of them are not usual quark-antiquark mesons, but are 'exotics', such as glueballs, hybrids, multi-quark states... Considering the large interest of the field, many new experi- ments will investigate it; thourough theoretical studies are thus quite necessary. In particular, our research is aimed at studying the scalar sector (up to now one of the less known), the nature of 2 (1440) (which is a good glueball candidate), charmonium and exotie states. In general, our goal is to produce clear predictions in order to allow future experiments to identify and classify exotics and qq mesons.