  Pionium lifetime corrections are evaluated in the frameworks of constrained
Bethe-Salpeter equation and chiral perturbation theory. Corrections of order
$O(\alpha)$ 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 $(6.1\pm 2.0)%$.
