We investigate the characteristics of intra-grain and grain boundary defects in polycrystalline Si films, by employing quantitative electron paramagnetic resonance measurements on liquid phase crystallized layers with an average grain size of 200 μm and tailored solid phase crystallized Si layers with similar intra-grain morphology but systematically varied grain sizes between 0.25 μm and 1 μm. The defect characteristics are found to be composed of two distinctive g -values of g = 2.0055 and 2.0032, which are attributed to grain boundary defects and intra-grain defects, respectively. Additional hydrogenation leads to a reduction of the overall defect concentration, while a rapid thermal annealing process primarily heals intra-grain defects. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.