SUMMARY  A variety of epidemiological sleep parameters was evaluated in 574 Finnish schoolchildren (age 7 to 17 years) and in their parents (454 mothers and 390 fathers). Three questionnaire forms were set, one for the pupil and two for his/her parents including information of sleep habits, disorders, and social background of the pupil and his/her family. The pupils were grouped by age (two preadolescent groups: 7.1–9.3 y and 9.4–13 y, adolescents 13.1–17.1 y) and sex. It was found that bedtime was more often after 22.00 hours among adolescents than preadolescents both at weekends and on weekdays. At weekends the wake‐up time was later in adolescents than preadolescents but on weekdays it was opposite in boys. On weekdays girls went earlier to bed than boys and woke up earlier than boys. Total sleep durations both on weekdays and at weekends were longer in preadolescent than in adolescent groups, and longer during weekend nights than on weekday nights in all groups. Girls experienced more dreaming and night waking, but boys snored more. Daytime sleepiness patterns were more common in adolescents than in preadolescents. Children who experienced daytime sleepiness more often had fathers with daily sleep urges. An association was found between age and sleep habits and some daytime sleepiness patterns; adolescents went to bed later and slept less, and had more problems with alertness during daytime than preadolescents. Some differences were also found between boys and girls. The daytime sleepiness of pupils correlated with the same symptom in fathers.