Cognitive behavioural therapy (CBT) is the most comprehensive means of medically treating obesity, but only few data have so far been published concerning its long-term effectiveness. We here report our experience of 1068 consecutive patients (868 females) treated with CBT at a university-based obesity centre. The patients were enrolled into three different programmes: a 14-week LEARN programme (672 patients), a 16-week MOB programme for the morbidly obese (259 patients), or a 20-week BINGE programme for subjects affected by binge eating (137 patients). Eighty-five percent of the subjects completed the weekly programmes. The percentage of patients attending the scheduled control visits during the 1-year follow-up gradually decreased, being very low in the BINGE group (10%). The percentage weight loss was an average of 6% during the weekly courses, being higher in the MOB programme; by the end of the weekly sessions, it exceeded 10% of initial body weight in 22% of cases and increased to 36% during the follow-up. The cumulative probability of follow-up was higher among the patients undergoing the MOB and LEARN programmes than among the BINGE patients (p < 0.0001), and decreased with the increasing severity of obesity. Female gender and a weight loss of > 10% i.b.w. increased compliance to follow-up. The study further demonstrates the difficulty of achieving compliance to chronic management of obesity and the critical role of binge eating disorder in the medium-term treatment of obesity. Strategies are needed to improve adherence to a follow-up protocol.