['To evaluate the impact of Roux-en-Y gastric bypass (RYGB) on quality of life in obese diabetic patients compared to standard medical therapy for type 2 diabetes mellitus.', 'We prospectively studied two matched obese populations with type 2 diabetes. Thirty patients underwent laparoscopic RYGB and 31 received standard medical therapy combined with a diabetes support and education program (DSE), consisting of educational sessions on diet and exercise. Groups were matched by age, gender, weight, glucostatic parameters, and use of glucose-lowering medications (oral agents and insulin therapy). Health-related quality of life (HRQOL) was assessed using the normalized SF-36 questionnaire, and data were collected at baseline and at 12-month follow-up.', 'Diabetic patients who underwent RYGB experienced a statistically significant increase in their overall HRQOL. However, the role-physical and mental health domains increased but did not reach statistical significance. Diabetic patients in the medical therapy and DSE group did not show any significant increase in HRQOL. The between-group differences for the HRQOL changes from baseline were significant, other than for role-physical and mental health domains. Percentage changes in glucostatic parameters, discontinuation of glucose-lowering medications, and T2DM remission were not found to predict the percentage change in SF-36 scores at 12\xa0months after RYGB.'] Does gastric bypass significantly improve quality of life in morbidly obese patients with type 2 diabetes?