OBJECTIVES To estimate the social cost of bariatric surgery techniques in obese patients with hypertension, diabetes mellitus (T2DM) and anxiety-depression disorders (ADD). METHODS A longitudinal multicenter study was conducted by enrolling obese adult patients in charge to 6 Hospital in Italy at time of intervention of gastric banding, gastric by-pass, and sleeve gastrectomy and following up to 1 year. Direct medical costs were estimated using tariffs for laboratory tests, diagnostic exams, visits, and prices for drugs. Procedure and inpatient cost data were collected at Center level. Non medical costs included costs for travel and accommodation, domestic help and informal care. The loss of productivity of patients have been estimated using the human capital approach. The incremental effects of having comorbidities on social costs were estimated by multivariate Generalized Linear Models (log link, Gamma family) adjusting for gender, age, BMI, type of intervention and complications. Costs are expressed in Euro 2013.   RESULTS Among 301 patients enrolled, 108 (36%) had hypertension, 53 (18%) T2DM and 47 (16%) ADD. The raw social cost of intervention were €8,749 (± €2,359), €9,511 (± €2,292) and €8,999 (± €2,275) for patients with hypertension, T2DM and ADD. A significant incremental effect of having T2DM was found on social cost of intervention (€751, 95%CI: 242-1,259, p=0.004). 1 year after intervention reductions of 48%, 81% and 15% were observed for hypertension, T2DM and ADD. The raw social annual costs estimated were € 2,461 (± € 1,490) for hypertension, € 2,424 (± € 951) for T2DM and € 3,582 (± € 2,017) for ADD. Direct non medical costs and indirect costs represent the main component of social cost in patients with hypertension and ADD. CONCLUSIONS Bariatric surgery led to reductions of obesity-related comorbidities. One year after, the economic burden is mainly sustained by patients, their families and the productivity system.