We evaluated changes in disease-specific quality of life (QOL) for children with sleep-disordered breathing (SDB). We conducted a cohort study in 69 children (age range, 6 months to 13 years; median age, 6.1 years) from a hospital-based pediatric otolaryngology practice in a metropolitan area. We used the OSA-18, an 18-item QOL survey with known test-retest reliability, internal consistency, and construct validity. Survey domains included sleep disturbance, physical suffering, emotional distress, daytime problems, and caregiver concerns. Tonsillectomy or adenoidectomy was performed as part of routine clinical care. The OSA-18 was completed at entry by the child's caregiver and again at least 4 weeks after surgery. The validity of the OSA-18 change score was assessed by comparison with multiple external constructs, including a validated measure of longitudinal change (OSD-6 survey). Responsiveness was assessed by the standardized response mean (SRM). The mean baseline OSA-18 survey score was 3.1 (SD, 0.9) of a maximum 7.0, with higher values indicating poorer QOL. Change scores were available for all children, with a mean interval between preoperative and postoperative surveys of 61 days (range, 42 to 92 days). The mean OSA-18 change score of 1.14 (SD, 0.71) showed significant correlation with tonsil size (r = 0.40), adenoid size (r = 0.31), OSD-6 change scores (r = 0.71), and the direct caregiver estimates of change (r = 0.34). OSA-18 change scores showed large responsiveness to change (SRM 1.44; 95% confidence interval, 1.16 to 69), with the most responsive domains being sleep disturbance, physical suffering, and caregiver concerns. Significant responsiveness was also demonstrated for the domains of daytime problems and emotional distress. The OSA-18 is a valid, reliable, and responsive QOL measure that combines the advantages of a discriminative and evaluative survey in a single instrument. The OSA-18 is a useful measure of patient-based outcomes for clinical trials, health services research, and routine clinical care.