In high intensity linear or circular accelerators space charge is not only a source of tune spread and shift, but also of various resonant phenomena. They may have an impact on lattice design, the choice of working points and/or or lead to beam degradation. Conclusive experimental data on the role of such space charge resonances are not easy to obtain - in some cases also comparison with theoretical models is challenging and a matter of discussion. In this talk, we first consider applications to high intensity linacs: the effects of space charge on halo coupling; and possibilities to work above the conventional 90 degrees longitudinal resonance stopband. For circular accelerators we discuss the issue of incoherent and coherent resonances, the effect of self-consistency and of Landau damping. Furthermore, second and higher order incoherent/coherent space charge resonances and their possible role in explaining recent observations of beam loss in the CERN PS are discussed.