['Sleep-disordered breathing (SDB) has been associated with impaired cognitive and behavioral function in school children; however, there have been limited studies in preschool children when the incidence of the disorder peaks. Thus, the aim of this study was to compare cognitive and behavioral functions of preschool children with SDB to those of non-snoring control children.', 'A clinical sample of 3-5 year-old children (primary snoring [PS], n=60; mild obstructive sleep apnea syndrome [OSAS], n=32; moderate/severe [MS] OSAS, n=24) and a community sample of non-snoring control children (n=37) were studied with overnight polysomnography. Cognitive performance and behavioral information were collected.', 'Children with PS and mild OSAS had poorer behavior than controls on numerous measures (p<.05-p<.001), and on some measures they had poorer behavior than the MS OSAS group (p<.05). In contrast, all groups performed similarly on cognitive assessment. Outcomes related more to sleep than respiratory measures.'] Is sleep-disordered breathing in preschool children associated with behavioral , but not cognitive , impairments?