Background : A comprehensive evaluation of bariatric surgery is required to inform decision-making. This will include measures of benefit and risk. It is possible that stakeholders involved with surgery value these outcomes differently, although this has not previously been explored. This study aimed to investigate and compare how professionals and patients prioritise outcomes of bariatric surgery. ; Methods : Systematic reviews and qualitative interviews created an exhaustive list of outcomes. This informed the development of a 130-item questionnaire, structured in four sections (complications of surgery; clinical effectiveness; signs, symptoms, and other measures; quality of life). Health professionals and patients rated the importance of each item on a 1–9 scale. Items rated 8–9 by at least 70 % of the participants were considered prioritised. Items prioritised in each section were compared between professionals and patients and interrater agreement assessed using kappa statistics (ĸ). ; Results : One hundred sixty-eight out of four hundred fifty-nine professionals (36.6 %) and 90/465 patients (19.4 %) completed the questionnaire. Professionals and patients prioritised 18 and 25 items, respectively, with 10 overlapping items and 23 discordant items (ĸ 0.363). Examples of items prioritised by both included ‘diabetes’ and ‘leakage from bowel joins’. Examples of discordant items included ‘re-admission rates’ (professionals only) and ‘excess skin’ (patients only). Poor agreement was seen in the ‘quality of life’ section (0 overlapping items, 8 discordant, ĸ −0.036). ; Conclusions : Although there was some overlap of outcomes prioritised by professionals and patients, there were important differences. We recommend that the views of all relevant health professionals and patients are considered when deciding on outcomes to evaluate bariatric surgery.