Recents advances on free radical polymeric photoinitiators (PP) are reported, with particular reference to structure-activity relations for systems applied to UV curable coatings. Benefits and drawbacks connected with the macromolecular nature of the above systems are discussed in comparison with the conventional low molecular weight (LMW) analogues. A classification is given depending on the type of photochemical mechanism they undergo for the generation of primary radicals under light irradiation. Some applications and future developments are also reported.