Abstract: The first line of treatment of obstructive sleep apnoea syndrome (OSAS) in children consists of adenotonsillectomy (T&A). The aim of the present study was to evaluate treatment outcomes of OSAS among obese children recruited from the community.A cross-sectional, prospective, multicentre study of Spanish obese children aged 3-14 years, with four groups available for follow-up: group 1: non-OSAS with no treatment; group 2: dietary treatment; group 3: surgical treatment; and group 4: continuous positive airway pressure treatment.117 obese children (60 boys, 57 girls) with a mean age of 11.3±2.9 years completed the initial (T0) and follow-up (T1) assessments. Their mean body mass index (BMI) at T1 was 27.6±4.7 kg·m(-2), corresponding to a BMI Z-score of 1.34±0.59. Mean respiratory disturbance index (RDI) at follow-up was 3.3±3.9 events·h(-1). Among group 1 children, 21.2% had an RDI ?3 events·h(-1) at T1, the latter being present in 50% of group 2, and 43.5% in group 3. In the binary logistic regression model, age emerged as a significant risk factor for residual OSAS (odds ratio 1.49, 95% confidence interval 1.01-2.23; p<0.05) in obese children surgically treated, and RDI at T0 as well as an increase in BMI emerged as significant risk factors for persistent OSAS in obese children with dietary treatment (OR 1.82, 95% CI 1.09-3.02 (p<0.03) and OR 8.71, 95% CI 1.24-61.17 (p=0.03)).Age, RDI at diagnosis and obesity are risk factors for relatively unfavourable OSAS treatment outcomes at follow-up.