Objective: The aim of the study was to evaluate the effectiveness of behavioral therapy in childhood obesity in metabolic outpatient clinic. Material and methods: Records of the 587 (289 boys) obese children in the age of 10.73 ± 3.57 were retrospectively analyzed (2005-2016). The therapy included lifestyle modification (increased physical activity, and support from the dietician and psychologist). Anthropometrical assessment was based on BMI z-score index. Results: Initial BMI z-score was higher in boys (3.29 SD vs. 2.66 SD, p < 0.00001). At follow-up visit for an average of 3 months, with a 66.8% of the children reported, an improvement was observed in 70% of them, and greater weight loss was found in boys (∆BMI Z-score: 0.28 SD vs.-0.15 SD). Improvement of the nutritional status (∆BMI Z-score) correlated with the age of children and the initial weight (vs. age: r = 0.233, p < 0.01; vs. BMI Z-score: r =-0.610, p < 0.00001). Further follow-up showed a reduction in the number of children continuing the treatment (at the 3 rd visit: 28.3%; at the 4 th visit: 19.1%; at the 5 th visit or more: 12.7%). In children, who remained under control of the outpatient clinic, a reduction in BMI z-score (p < 0.00001) was observed from the 3 rd visit. Conclusions: Behavioral therapy on the outpatient clinic level is effective, but its effectiveness is pointedly reduced by the high number of children and their parents who avoid the treatment or refuse to continue this model of therapy. The essential challenge is to keep the motivation of both parents and children. Key words: childhood obesity, behavioral treatment, BMI, outpatient clinic. 3.7% girls and 3.6% boys [3,4], and this is the reason why we should pay special attention to these children in clinical practice. In consequence, they are likely to stay obese in future. The obesity epidemic is a serious and growing problem for public health systems worldwide [5-7], affecting all age groups including very young children [8]. The main and the most important problem of obesity are the short-and long-term consequences. Obesity can lead to numerous comorbidities such as diabetes mellitus type 2, hypertension, hyperlipidemia, or metabolic syndrome [8,9]. These progressive disorders lead to decline life expectancy. Regardless of multiple organic diseases, obesity often conduce to psychological distresses because is inevitably accompanied by discrimination and stigmatization