Both sleep problems and depression are common problems in adolescence, but well-defined large epidemiological studies on the relationship are missing in this age group. The aim of this study was to examine the association between depression and several sleep parameters, including insomnia, in a population-based study of adolescents aged 16-18 years, and to explore potential gender differences. A large population-based study in Hordaland County in Norway conducted in 2012, the ung@hordaland study, surveyed 10,220 adolescents aged 16-18 years (54% girls) about sleep and depression. The sleep assessment included measures of the basic sleep parameters for weekdays and weekends. Depression was defined as scoring above the 90th percentile on the total score of Short Moods and Feelings Questionnaire (SMFQ). There was a large overlap between insomnia and depression in both genders and across depressive symptoms. Depressed adolescents exhibited significantly shorter sleep duration and time in bed as well as significantly longer sleep onset latency (SOL) and wake after sleep onset (WASO). Adolescents with insomnia had a 4- to 5-fold increased odds of depression compared to good sleepers. There was also a significant interaction between insomnia, sleep duration and depression, with a more than eightfold increase in odds of depression for those who met criteria for insomnia and who slept <6 h. These associations held for both genders, but were stronger in boys. To the best of our knowledge, this is the first population-based study to investigate sleep and insomnia in relation to depression among adolescents. The findings call for increased awareness of sleep problems and depression as a major public health issue.