  In this paper we consider the diphoton production in hadronic collisions at
the next-to-next-to-leading order (NNLO) in perturbative QCD, taking into
account for the first time the full top quark mass dependence up to two loops
(full NNLO). We show selected numerical distributions, highlighting the
kinematic regions where the massive corrections are more significant. We make
use of the recently computed two-loop massive amplitudes for diphoton
production in the quark annihilation channel. The remaining massive
contributions at NNLO are also considered, and we comment on the weight of the
different types of contributions to the full and complete result.
