Fluorine-18-fluorodeoxyglucose positron emission tomography (FDG-PET) is a useful diagnostic tool for the staging of patients with multiple myeloma (MM). The aim of this study is to perform a systematic review of the usefulness of FDG-PET or PET/CT in monitoring response to treatment in patients with MM. A comprehensive computer literature search of the PubMed/MEDLINE, Scopus and Embase databases was carried out to identify relevant peer-reviewed articles on the use of FDG-PET or PET/CT in monitoring the response to treatment in patients with MM. Ten studies described investigations of the role of FDG-PET or PET/CT in monitoring the response to treatment in 690 patients with MM or solitary plasmacytoma: six of these were conducted prospectively, while four studies were retrospective. These articles were retrieved in full-text version and analyzed. Based on these findings from the literature, FDG-PET or PET/CT appear to be useful in the assessment of treatment response in patients with MM.