We compute the two-loop QCD corrections to the neutral Higgs-boson masses in
the MSSM, including the effect of non-vanishing external momenta in the
self-energies. We obtain corrections of O(alpha_t*alpha_s) and
O(alpha*alpha_s), i.e., all two-loop corrections that involve the strong gauge
coupling when the only non-vanishing Yukawa coupling is the top one. We adopt
either the DRbar renormalization scheme or a mixed OS-DRbar scheme where the
top/stop parameters are renormalized on-shell. We compare our results with
those of earlier calculations, pointing out an inconsistency in a recent result
obtained in the mixed OS-DRbar scheme. The numerical impact of the new
corrections on the prediction for the lightest-scalar mass is moderate, but
already comparable to the accuracy of the Higgs-mass measurement at the LHC.Comment: 22 pages, 5 pdf figures; v2: version to appear in EPJ