[en] In the first part of the talk, the properties of the ρ-meson in nuclear matter are discussed. In an effective hadronic model the modification of the pion cloud at finite baryon density due to mixing of the pions with delta-particle-nucleon-hole states is computed. This leads to a strong increase of the ρ-meson width while its mass remains almost constant. In the second part of the talk, the diffractive production of ρ- and ω-mesons from protons and nuclei with high energy photons (E_γ>3 GeV) is reviewed and the sensitivity of this process to changes in the ρ-mesons mass is discussed. Finally, a model for photoproduction of ρ- and ω-mesons at lower energy (E_γ<2 GeV), on proton targets is presented. (orig.)