To systematically review the literature data on the role of Fluorine-18-fluorodeoxyglucose positron emission tomography and positron emission tomography/computed tomography (FDG-PET and PET/CT) in patients with retroperitoneal fibrosis (RF), PubMed/MEDLINE, Embase and Scopus databases were searched for articles that evaluated the usefulness of FDG-PET and PET/CT in patients with RF from inception to March 31, 2012. Review articles or editorials, articles not in the field of interest of this review, case reports and preclinical studies were excluded. Only studies including FDG-PET or PET/CT scans performed in at least three patients with RF were included. Ten studies comprising a total of 101 patients with RF were found. The main findings of the included studies are described. FDG-PET and PET/CT are feasible and suitable imaging methods for evaluating patients with RF. These functional imaging techniques seem to be useful both in the diagnosis (mainly in the assessment of activity and extent of the disease) and in evaluating the treatment response in patients with RF. Given the heterogeneity among the various studies for PET analysis and diagnostic criteria, a standardization of the technique is required in order to achieve reproducible and inter-observer independent results. Moreover, further studies are needed to substantiate the role of FDG-PET and PET/CT in patients with RF.