  We present the full ${\cal O}(\as^2)$ computation of the interference effects
between the Higgs diphoton signal and the continuum background at the LHC.
While the main contribution to the interference originates on the $gg$ partonic
subprocess, we find that the corrections from the $qg$ and $q\bar{q}$ channels
amount up to 35% of it. We discuss the effect of these new subprocesses in the
shift of the diphoton invariant mass peak recently reported by S. Martin in
Ref.\cite{Martin:2012xc}.
