Strong evidence for successful and cost-effective obesity management strategies is still generally lacking, leading the medical profession to rely increasingly on surgical options to treat obesity in children and adolescents. We performed a systematic review to examine the effectiveness of surgical interventions to treat obese children and adolescents, and whether they are cost-effective. We searched PubMed, ISI Web of Science, Embase and the Cochrane Library to 6 September 2010, and hand-searched bibliographies. We included articles with English abstracts if they examined subjects ≤19 years of age, reported at least one postoperative weight loss measure and at least 1 year of postoperative follow-up. Thirty-seven relevant papers on bariatric surgery effectiveness in 831 children or adolescents were included, spanning 36 years. Thirteen studies examined gastric banding, with mean body mass index (BMI) reductions ranging from 8.5 to 43 kg m−2. Weight gain was reported in one case study. Eight papers examined Roux-en-Y gastric bypass, with mean BMI reductions ranging from 9 to 25 kg m−2. Fourteen publications studied other forms of bariatric surgery: sleeve gastrectomies, vertical banded gastroplasty, biliopancreatic diversion or a combination of procedures. Mean BMI reductions ranged from 9 to 24 kg m−2. Three surgery-related mortalities were reported, as was weight regain in several cases. The majority of studies reported resolution or improvement of comorbid conditions. A range of postoperative complications were identified across surgery types, including: ulcers, intestinal leakage, wound infection, anastomotic stricture, nutritional deficiencies, bowel obstruction, pulmonary embolism, disrupted staple lines, band slippage, psychological intolerance and repeated vomiting. Evidence on cost-effectiveness was limited to one Australian modelling project, which deemed laparoscopic adjustable gastric banding cost-effective for adolescents. Existing evidence – although based generally on underpowered, retrospective studies – suggests that bariatric surgery in older children results in significant weight loss and improvements in comorbidities and quality of life. However, postoperative complications, compliance and follow-up may be more problematic in adolescents than adults, and availability of long-term data on safety, effectiveness and cost-effectiveness remains largely unknown. Pending an improvement in the quality of available evidence, a cautious approach to child and adolescent bariatric surgery is warranted, and reversible techniques are advisable compared to approaches that permanently alter anatomy.