BACKGROUND: This study was designed as an economic evaluation alongside a randomized clinical trial. The object of this study was to evaluate the 1-year cost-effectiveness of surgical treatment of morbid obesity comparing two operations. METHODS: 100 patients were assigned randomly to vertical banded gastroplasty (VBG) or Lap-Band surgery. Both medical and non-medical costs were identified and measured. Costs data were combined with percentage Excess Weight Loss (%EWL) and with Quality Adjusted Life Years (QALYs) to obtain cost per %EWL and cost per QALY ratios. RESULTS: At 1 year, the total costs were not significantly different between both groups (95% confidence interval E5,999-E1,765). Also, the QALY gain after surgery was not significantly different between the two groups. However, %EWL was significantly higher in the VBG group compared to the Lap-Band group, P-value .0001. The estimated incremental cost per %EWL was E105.83 (E1,885.91/-17.82). For the costs per QALY, the estimated ratio was dominant. The overall mortality in this study was 2%. 2 patients in the VBG group died within 30 days after surgery; 1 of these deaths was possibly related to the VBG procedure. CONCLUSION: At 1 year after surgery, the costs and QoL of the two treatment modalities were found to be equal. Therefore, the selection of the procedure can be based on the clinical aspects, effectivity and safety at 1 year. In addition, the results of a long-term cost-effectiveness analysis (e.g. with a follow-up of 36 months) planned in the future can also be helpful in the selection of the preferred treatment.