ABSTRACT:The objective of this study was to quantify behavioral and attention capacity changes in children aged 4 -11 y before and 3 mo after adenotonsillectomy (A/T). Overnight cardiorespiratory recordings were performed in 61 "behaviorally normal" children 1 wk before A/T. Tests of sustained attention using visual and auditory continuous performance tests (CPT) were completed by children 1 wk before and 3 mo after A/T. Behavioral Assessment Scales for Children (BASC) and a sleep questionnaire were completed by the parent/s at these same times. Results from overnight cardiorespiratory recordings showed that the children had mild sleeprelated breathing disorders (SRBD) preoperatively with a mean apnea/hypopnea index of 3.0/h and a movement awakening index of 2.5/h. The majority had parent-perceived sleep and breathing difficulties that significantly improved post-A/T. BASC T scores for externalizing and internalizing behaviors improved post-A/T, e.g., behavioral symptom index mean pre-A/T was 56.2 (95% confidence interval, 52.8 -59.6) compared with 50.9 (48.5-53.5) post-A/T. Some measures indicative of impulsivity and attentiveness obtained from the visual CPT before surgery, improved post-A/T, but no change was observed in any auditory CPT measures. Our data confirm improvements in subjective measures of sleep problems in children treated for SRBD and strengthen the notion of treating the disorder, not only related to the obvious clinical condition but also to the underlying sleep problems and adverse effects on daytime behavior and attention. (1), with snoring, difficulty breathing, apnea, and persistent mouth breathing that ranges from primary snoring, through upper airways resistance syndrome, to OSA. The most common treatment for children with adenotonsillar hypertrophy or recurrent tonsillitis is A/T. This has been shown to result in clinical improvement in the majority of cases. In severe cases involving OSA, failure to treat can be associated with serious morbidity such as failure to thrive and systemic hypertension, and pulmonary hypertension with or without cor pulmonale can develop (1).SRBD have been linked to daytime behavioral problems, predominantly those associated with hyperactivity, aggression, and inattention (2-4), and poorer performance on tests of memory and intelligence (5). At short-term follow-up after treatment, significant improvements in children's vigilance and behavior in areas of aggression, inattention, impulsivity and hyperactivity (6,7), and quality of life (8) have been reported. Also reported are short-term improvements in several cognitive factors such as perceptual closure, inference, organization, visual and auditory short-term memory, ability to solve problems and think analytically (9), and learning 1 y after treatment for a SRBD in poor academic achievers (10).The main physiologic characteristics during sleep for children with SRBD are intermittent hypoxemia associated with frequent apneas, hypopneas and sleep fragmentation due to frequent arousals, awakenings, and a red...