A QCD analysis of the reactions A B \to \gamma ^* \gamma and \gamma ^* \gamma \to AB in the forward region shows that they can be factorized in a way which is quite similar to the framework developped for deeply virtual Compton scattering. The generalized parton distributions (GPDs) related to this latter process are being replaced by new non perturbative hadronic matrix elements, the transition distribution amplitudes (TDAs).

PACS numbers: 13.60.--r, 13.88.+e