The basis for resonant photoemission is discussed in connection with data for a physisorption system, Ar/Pt(111) and a 3d transition metal, Ni(100). For Ar/Pt(111) the quasi-localized character of the intermediate state leads to two types of features in the autoionization spectra, showing resonant Raman and normal Auger-like behaviour, respectively. For Ni(100) resonant Raman behaviour is observed in photoemission below the L3 threshold. At threshold, the emission feature changes character and after a rather narrow transition region it appears at constant emission energy instead. Clear signatures of interference between the direct photoemission and autoionization channels are identified.