  The present status of the theoretical estimates of the difference between the
widths of the neutral Bs-mesons and of the B-meson lifetime ratios is reviewed.
In particular, the lattice results for the matrix elements of the relevant
(delta B=2)-operators are updated and the first lattice QCD results for the
matrix elements of (delta B=0)-operators are presented. In both cases, the NLO
perturbative QCD corrections in the coefficient functions have been included.
The theoretically updated results are: (delta Gamma/Gamma)_{Bs} = (7 +/- 4) %,
tau(B+)/tau(Bd) = 1.07(3) and tau(Bs)/tau(Bd) = 1.00(2).
