Pionium lifetime corrections are evaluated in the frameworks of constrained
Bethe-Salpeter equation and chiral perturbation theory. Corrections of order
O(α) are calculated with respect to the conventional lowest-order
formula, in which the strong interaction amplitude has been calculated to
two-loop order with charged pion masses. The total correction is found to be of
the order of (6.1±2.0).Comment: 9 pages, Latex. Uses Dubna98.sty. Talk given at the Int. Workshop
"Hadronic Atoms and Positronium in the Standard Model", Dubna, 26-31 May
1998. To appear in the Proceeding
