['To study emotional and behavioral problems and sleep and cognitive performance in snoring and nonsnoring 3- to 6-year-old children.', 'As part of an epidemiological study of sleep disordered breathing (SDB) in preschool-aged children, 43 snorers and 46 nonsnorers participated in a clinical study. Their parents completed the Child Behavior Checklist (CBCL). The children were assessed with Wechsler Preschool and Primary Scale of Intelligence, Revised and subtests of the Developmental Neuropsychological Assessment (NEPSY-A) representing aspects of attention, language skills, sensorimotor functions, memory, and learning.', 'On the CBCL snoring children had significantly more parent reported internalizing symptoms (p < .05) than the nonsnoring children, especially symptoms of anxious/depressed mood (p < .01) and emotional reactivity (p < .05). More children from the snoring group than from the nonsnoring group (22 vs 11%) scored in the subclinical or clinical range on the internalizing scale. Interestingly, no significant difference between the groups was found in the amount of externalizing symptoms. The amount of sleep problems other than snoring was higher in the snoring than in the nonsnoring group (p < .01). On tests measuring auditory attention (p < .01) and language skills (verbal IQ, p < .05), the snoring group performed worse than the nonsnoring group.'] Is mood associated with snoring in preschool-aged children?