The goal of the study was to assess the effectiveness of cognitive behavioural therapy (CBT) of obesity in the sense of attainment and keeping not only of weight losses but also the changes in subjective evaluation of quality of life. CBT is applied during twelve weeks courses of weight losses with a structured programme. The sample of women leavers of the courses in 1994-1999 was chosen for this study, thus they finished their first course two to seven years ago. 803 questionnaires were delivered, 538 answers were gained, and the return was 67 per cent. The average age of participants was 45.3 years, the average weight at the beginning of the course was 86.3 kg, and BMI was 31.2. The women leavers of weight losses courses lost in average 6.4 kg in 12 weeks what is 7.4 per cent of entry weight, about half of participants was successful in keeping of weight losses. Two thirds of courses participants had after 2 to 7 years since leaving the course lower weight than when entering the course, 40 per cent kept at least 5 per cent of the weight loss what has already a positive health impact. The cause of the success was that the method leading to the change of the life style was acceptable because only in that way the change can be lasting. In more than half of participants it led to increasing quality of life. Three quarters of them kept this increased quality of life (withdrawal of health and mental problems, enlargement of social activities, change in the rank of life values, the bettering in the relation to own body).