2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/48058We review the existing theoretical approaches to the study of the observables of hadronic atoms. In the relativistic perturbative approach based on the Bethe-Salpeter equation and Chiral Perturbation Theory we derive the general expression for the pi+pi- atom lifetime. The lowest-order correction to the relativistic Deser-type formula for the atom width is predicted to be 6.1\pm 3.1 %.7 pages, LaTeX-file (dubna98.sty) Talk given at the International Workshop "Hadronic Atoms and Posirtonium in the Standard Model", 26-31 May 1998, Dubna, RussiaHigh Energy Physics - Phenomenologytext