Background and Aims: Bariatric surgery is the most effective treatment for obesity. However, not all patients have similar weight loss following surgery and many researchers have attributed this to different pre-operative psychological, eating behavior, or quality-of-life factors. The aim of this study was to determine whether there are any differences in these factors between patients electing to have bariatric surgery compared to less invasive non-surgical weight loss treatments, between patients choosing a particular bariatric surgery procedure, and to identify whether these factors predict weight loss after bariatric surgery. Material and Methods: This was a prospective study of 90 patients undergoing gastric bypass, vertical sleeve gastrectomy, or adjustable gastric banding and 36 patients undergoing pharmacotherapy or lifestyle interventions. All patients completed seven multi-factorial psychological, eating behavior, and quality-of-life questionnaires prior to choosing their weight loss treatment. Questionnaire scores, baseline body mass index, and percent weight loss at 1 year after surgical interventions were recorded. Results and Conclusions: Surgical patients were younger, had a higher body mass index, and obesity had a higher impact on their quality of life than on non-surgical patients, but they did not differ in the majority of eating behavior and psychological parameters studied.