High energy protons are accompanied by a flux of Weizsaecker-Williams photons, which can induce photon-photon and photon-hadron
reactions. Due to the spin one of the photon such processes contribute to final state topologies with large rapidity gaps.
For example the central exclusive production of vector mesons can be thought of as a photon-Pomeron fusion.
For heavy vector mesons, like $J/\psi$, the coherent diffractive production opens an access to the (unintegrated) gluon distribution at very small x. We present an analysis of $J/\psi$ and $\psi'$ production including absorptive corrections
on the amplitude level.
Important contributions to central production with gaps come from proton dissociative processes. In the case of dilepton production
via $\gamma-\gamma$ fusion, they are calculable in terms of the proton structure functions. We discuss an approach based on a generalization of $k_T$-factorization.