OBJECTIVE: To measure the effects of cognitive-behavioural therapy on health-related quality of life (HRQL) in obese patients, in relation to binge eating disorder. DESIGN: Longitudinal, clinical intervention study consisting of structured sessions of cognitive-behavioural therapy, preceded by sessions chaired by a psychologist in subjects with binge eating. SUBJECTS: Two groups of obese patients (92 treated by cognitive-behavioural therapy (77 females); 76 untreated controls (67 female), selected from the waiting list (control group)). Of 92 treated patients, 46 had a binge eating disorder at psychometric testing and structured clinical interview. MEASUREMENTS: Health-related quality of life by means of Short-Form 36 questionnaire at baseline and after 3-5 months. RESULTS: Cognitive-behavioural treatment produced an average weight loss of 9.4 ± 7.5 kg, corresponding to a BMI reduction of 3.48 ± 2.70 kg/m2. No changes were observed in the control group. All scales of HRQL improved in treated subjects (by 5-19%). In obese subjects with binge eating weight loss was lower in comparison to non-bingers (7.7 ± 8.1 vs 11.1 ± 6.6; P = 0.034). However, the improvement in HRQL was on average larger, and significantly so for Role Limitation - Physical (P = 0.006), Role Limitation - Emotional (P = 0.002), Vitality (P = 0.003), Mental Health (P = 0.032) and Social Functioning (P = 0.034). Bodily Pain was the sole scale whose changes paralleled changes in body weight. CONCLUSIONS: The positive effects of cognitive-behavioural therapy, mainly in subjects with binge eating, largely outweigh the effects on body weight, resulting in a significant change in self-perceived health status.