OBJECTIVES: Results of gastric restrictive surgery as treatment modality for morbid obesity are supposed to have with a great impact on QoL. In a RCT the long-term-effectiveness of VBG and the LapBand-surgery were assessed. An interim analysis using determinants of first-year QoL after both types of surgery is presented. METHODS: Sixty-three morbidly obese patients were evaluated one-year after surgery. QoL and BMI were assessed preoperatively as well as 3, 6, and 12 months postoperatively. Furthermore, (post) surgery-related problems were assessed during the same time period. QoL was measured using EQ-VAS. ANCOVA-analysis for repeated measures was used to analyse the effects on QoL. RESULTS: Thirty-one patients (age 38.1 ± 7.7) underwent VBG and 32 patients (age 36.3 ± 11.0) underwent LapBand-surgery. Controlled for age and gender in both groups BMI decreased and EQ-VAS increased significantly. Interestingly, first-year linear increase in EQ-VAS cannot be related to the type of surgery undergone. There are, however, two statistically significant interactions in which type of surgery is involved: one with first-year linear decrease in BMI and one with first-year linear increase in surgery-related problems. Only in the VBG-group both linear decrease in BMI and linear increase in surgery-related problems have an effect on the increase of EQ-VAS (Beta=-.499 p<.001 and Beta=-.354, p=.006 respectively). CONCLUSION: A possible explanation for the more complicated relationship of the decrease in BMI and increase of EQ-VAS in the LapBand-group can be that these patients have more surgery-related problems in the first year after surgery. The general relationship between increase in surgery-related problems on the increase of EQ-VAS is unclear. A possible explanation can be a shifting of priorities for patients: once weight loss in VBG-patients is secured, post-surgery problems may become relevant in explaining the differences in EQ-VAS. Surgery-related problems may only become relevant, if considerable weight loss is experienced.