Aims: The aim was to investigate changes in child and adolescent sleep habits in Sweden over time. This had not been done previously. Methods: Cross-sectional questionnaire data over three decades of investigations of the Health Behaviours of School Children study (1985/1986, 2005/2006 and 2013/2014) were used. The sample included 18,682 children and adolescents, aged 11, 13 and 15. Empirically based age-specific sleep duration recommendations were used to operationalise sleep duration. Results: The results showed that, over time, fewer go to bed early and more go to bed late. Regarding sleep duration, there have been decreases in the proportion of children and adolescents that sleep as much as is recommended for their age. Sleep onset difficulties have increased for all ages and increase the odds of sleeping less than recommended as well as having late bedtimes. Boys were more likely than girls to have later bedtimes and to sleep less than recommended. A vocational educational track, not planning to study further or being unsure of which track to choose increased the odds for 15 year olds to have late bedtimes and to sleep less than recommended compared with a college preparatory track. Conclusions: The results indicate that over time, fewer children and adolescents attain sufficient sleep duration. This may have implications for study results, mental health and cognitive abilities.