Pigment epithelial-derived factor (PEDF) is a 50-kDa secreted glycoprotein that belongs to the non-inhibitory serpin. It has an α/β core serine-protease inhibitor domain, 3 major β-sheets, and 10 α-helices. Although PEDF does not inhibit either serine or cysteine proteinases, PEDF exerts diverse physiological activities including anti-angiogenesis, anti-vasopermeability, anti-tumor, and neurotrophic activities. Recent studies have shown that a variety of peptides derived from PEDF possess activities similar to those of the parent molecule through interactions with the extracellular matrix, binding to PEDF receptors, nuclear localization and phosphorylation. Thus, peptides derived from PEDF have therapeutic potential for various diseases and therefore, it is important to clarify the structure-function relationship of PEDF. In this review, we summarize structural features of PEDF that could affect various target organs such as blood vessels, tumors, and the central nervous system. In addition, since PEDF is recently identified as a regulator for glucose and lipid metabolism, we also discuss PEDF structures specially related to insulin-sensitizing and triglyceride-reducing properties.