Pre-surgical psychosocial evaluation of bariatric surgery (BS) patients should identify psychiatric issues that could worsen after surgery and those requiring additional ongoing intervention. In this view, the use of reliable, appropriate and concise evaluating instruments is of critical importance. The aim of the present study was to investigate the clinical utility of both the Symptom Checklist 90-Revised (SCL-90-R) and its brief unidimensional version, the so-called Symptom-Checklist-K-9 (SCL-K-9) in detecting the presence of psychiatric disorders among bariatric surgery (BS) candidates.