Diffractive hadronic interactions include a set of processes that are
known since a long time although their inclusion in a QCD framework
represented always a challenge. In the last years many improvements in the
understanding of this kind of physics has been carried out at the HERA
collider in DESY Hamburg. A particularly important role in the
understanding of diffraction is played by dijets and other hard-scale
processes. The talk will first introduce shortly the physics carried out
at HERA with a particular focus on diffraction and then will expose the
recent results in diffractive physics in presence of jets.