OBJECTIVE To estimate the prevalence of self-reported sleep problems, to examine associations among demographic characteristics, familial factors, and sleep problems, and to investigate the association between the symptoms of obstructive sleep apnea (OSA) and nonorganic sleep disorders. METHODS An anonymous questionnaire with 22 questions was designed. 332 schoolchildren (aged 11-15 years, mean age 12 years and 9 months; median, 12 years; 56% female, 44% male) from two high schools in Vienna were investigated with regard to self-reported symptoms characteristic for obstructive sleep apnea and for parasomnia/insomnia. Data were analyzed by definition of three groups (problem, occasional problem, and nonproblem sleepers, and by calculation of an insomnia/parasomnia sum score). Statistical analysis included nonparametric tests (Mann Whitney-U and Kruskal), Pearson correlation test, and multiple regression analysis. RESULTS Twelve percent reported at least one sleep problem every night, 76% reported occasional sleep problems, and 12% had no sleep problems. Girls were affected more frequently than boys (p <.01). Children with sleep problems suffered more often from concentration difficulties (p <.05), daytime fatigue (p <.001), and daytime naps (p <.05). Children who snored had nightmares (10% vs. 2%, p <.01), night terrors (4% vs. 1.5%, p <.001), sleepwalking (1.4% vs. 1%, p <.05), and nocturnal awakening (16% vs. 5%, p <.01) more frequently. On multiple regression analysis, 23% of the variability of a defined parasomnia/insomnia sum score had the characteristic OSA symptoms of nocturnal sweating, dryness of the mouth, snoring, hyperactivity, and daytime fatigue. CONCLUSIONS 12% of schoolchildren aged 11-15 years reported sleep problems almost every night. The children suffer from daytime fatigue, naps, and concentration difficulties. Nearly one-fourth of the symptoms of parasomnia/insomnia were associated with characteristic signs of OSA, suggesting the importance of a routine clinical investigation in children with so-called nonorganic sleep disorders.