Objective: This study was conducted to better define clinical results and understand factors determining responsiveness to surgical treatment for neurogenic thoracic outlet syndrome (NTOS) in adolescent and adult populations. Methods: A retrospective review was conducted for 189 patients with disabling NTOS who underwent primary supraclavicular decompression (scalenectomy, brachial plexus neurolysis and first rib resection, with or without pectoralis minor tenotomy) from April 2008 to December 2010. Clinical characteristics were compared between 35 adolescent patients (aged <21 years) and 154 adults (aged >21 years). Functional outcome measures were assessed before surgery and at 3- and 6-month follow-up using a composite NTOS Index combining the Disabilities of the Arm, Shoulder and Hand (DASH) survey, the Cervical-Brachial Symptom Questionnaire (CBSQ), and a 10-point visual analog scale (VAS) for pain. Results: Adolescent and adult patients were not significantly different with respect to sex (overall 72.5% female), side affected (58.7% right, 60.3% dominant limb), bony anomalies (23.3%), previous injury (55.6%), coexisting pain disorders (11.1%), and positive responses to scalene muscle anesthetic blocks (95.6%). Compared with adults, adolescent patients had a significantly (P <.05) lower incidence of depression (11.4% vs 41.6%), motor vehicle injury (5.7% vs 20.1%), previous operations (11.4% vs 29.9%), preoperative use of opiate medications (17.1% vs 44.8%), and symptom duration >2 years (24.2% vs 50.0%). Mean preoperative NTOS Index (scale 0-100) was significantly lower in adolescent vs adult patients (46.5 ± 3.6 vs 58.5 ± 1.7; P =.009), and hospital length of stay was 4.4 ± 0.2 vs 4.9 ± 0.1 days (P =.03), but the rate of postoperative complications was no different (overall, 4.2%). Although both groups exhibited significant improvement in functional outcome measures at 3 and 6 months, adolescent patients had significantly lower NTOS Index (10.4 ± 3.1 vs 39.3 ± 3.3; P <.001) and use of opiate medications (11.4% vs 47.4%; P <.001) compared with adults. Conclusions: Adolescents undergoing supraclavicular decompression for NTOS had more favorable preoperative characteristics and enhanced 3-month and 6-month functional outcomes than adults. Further study is needed to delineate the age-dependent and independent factors that promote optimal surgical outcomes for NTOS.