The study found that boys played computer games and used the Internet more often than girls, whose mobile phone usage was more intensive than boys' use. Intensive use of ICT was linked with perceptions of poor health, particularly when ICT use negatively affected sleeping habits. Poor sleeping habits were associated with increased waking-time tiredness. These associations were gender-specific, especially among older adolescents (16-year-olds and 18-year-olds). Intensive computer use was a risk for boys' health, and intensive mobile phone use posed a risk for girls' perception of poor health. Participants were 7,292 Finnish adolescents derived from a nationally representative sample of 12-, 14-, 16- and 18-year-olds collected in 2001. Participants completed a structured mailed questionnaire and returned it by prepaid mail. The use of ICT was conceptualized by two dimensions: the use of a computer (Internet surfing and playing digital games) and mobile phone use. Sleeping habits were indicated by sleeping hours and regularity of bedtime; waking-time tiredness was indicated by feeling active in the morning and daytime sleepiness; and perceived health was measured by health status, health complaints, and musculoskeletal symptoms. 4 tables, 3 figures, and 74 references