Obesity, especially morbid obesity, is a major health problem with considerable impact on physical, mental and social quality of life. Assessment of quality of life is considered crucial to understand and evaluate the consequences of obesity. However, the heterogeneity of the quality of life concept makes it difficult to compare and value studies on quality of life. Both generic -applying to any disease- and obesity specific quality of life instruments can be used as assessment instruments in obesity. Generic instruments have the advantage that they can be used to compare the quality of life consequences of divergent diseases, whereas the major advantage of obesity specific instruments is that these are more sensitive to changes in obesity. Obesity has major consequences for quality of life, as a result of co-morbidities of obesity, weight stigmatization, and other less frequently ventilated problems. Bariatric surgery has been proven to lead to significant weight loss and improvement of quality of life. Instruments differ in the suitability to assess quality of life after surgery and weight loss, and they differ in the domains of quality of life that are tapped by the instruments. Besides obesity, also personal and psychosocial variables influence quality of life and affect the outcome of surgery. Obesity, even after substantial weight loss by gastric bypass surgery, is a chronic disease requiring life long consideration, in order to attain long standing quality of life improvement.