Objective ·To quantify the volume of quadrigeminal cistern arachnoid cysts (QACs) and hydrocephalus indicators, and analyze the clinical features of QACs in children and the efficacy of different surgical techniques, with the goal of improving understanding, diagnosis, and treatment of this condition. Methods ·A retrospective analysis was conducted on 27 pediatric patients with QACs treated at Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, between January 2015 and June 2025. The volume of QACs and the Evans index were calculated by using cranial magnetic resonance imaging (MRI) and computed tomography (CT). Clinical data, including demographics, symptoms/signs, imaging findings, surgical procedures, and follow-up outcomes, were reviewed. Results ·The cohort (age range: 0 d‒150 months; male-to-female ratio: 1.08∶1) had a median preoperative QAC volume of 34 402 (15 022, 138 478) mm³ and a median Evans index of 0.29 (0.24, 0.48). Among the cases, twelve were asymptomatic and were predominantly infants under 6 months of age, whereas fifteen symptomatic cases—presenting with intracranial hypertension, seizures, limb weakness, or frequent blinking—were mostly older than 6 months. A total of 33 surgeries were performed (one surgery: 22 cases; two surgeries: 4 cases; three surgeries: 1 case). Reoperation rates were 15.8% for endoscopic fenestration (EF), 40.0% for EF combined with endoscopic third ventriculostomy (ETV), and 0 for ventriculoperitoneal shunt (VP). The overall reoperation rate was 18.5%, with infants under 6 months having a higher probability of requiring repeat surgeries. During follow-up, 88.9% of patients showed significant QAC volume reduction at 3 months postoperatively, and 92.3% exhibited clinical improvement. No efficacy differences were found among EF, EF+ETV, and VP procedures to date. Patients with larger preoperative QACs (≥50 000 mm³) showed more pronounced reductions in QAC volume and Evans index at 12 and 24 months postoperatively. Conclusion ·QACs exhibit no gender predilection and may present with limb weakness or frequent blinking as initial symptoms. Age and symptoms may be correlated. Surgical outcomes are favorable, with low reoperation rates, significant short-term volume reduction, and symptom resolution. No difference in efficacy is observed among EF, EF+ETV, and VP procedures. Larger QACs are associated with a better long-term prognosis.