Background: The Strengths and Difficulties Questionnaire (SDQ) measures behavioral problems among children and adolescents. Prior research in Sweden has included child self-report or parent ratings from community or population data. Objective: To provide child-reported and parent-rated SDQ norms for 11-to 16-year-olds, as well as data on child-parent agreement and parental sociodemographic correlates: education, employment status, and quality of life. Method: A random population sample with 600 children aged 11 to 16 years, 100 per age group, and one of their parents (N=1200) yielded a sampling pool of 1158 participants and a 34.8% response rate, including 175 child-parent pairs and 27 and 26 child/parent singletons. Responses to child and parent versions of the extended SDQ were analyzed by child gender and age. Child-parent agreement was evaluated using the Prevalence-and Bias-Adjusted Kappa and Bland-Altman plots. Results: Older children reported greater difficulties compared with younger children, while girls reported a higher negative impact of difficulties on daily life in comparison to boys. Child-parent item-by-item agreement was fair to slight on 15 of the 25 SDQ items, perfect to moderate on 9 items, and less than chance on 1 item, but generally high regarding dichotomous assignment to the "raised difficulties" or "normal" groups, based on subscales and the total SDQ score. Greater difficulties for children were reported by parents born outside Sweden, parents of children born outside Sweden, parents lacking regular employment, and parents with lower education or lower quality of life. In relation to other child-parent pairs, parents born outside Sweden perceived greater difficulties for their children compared with the children's own ratings. Parents with better physical health and social relationships rated their children as having fewer difficulties compared with the rates reported by children. Conclusions: Gender differences contrasted with prior Swedish studies showing higher ratings for boys on hyperactivity and total difficulties and for girls on emotional symptoms. However, findings on increased difficulties with age concurred with prior studies. Research on children's mental health should be widely and systematically conducted at regular intervals and encompasses large, representative samples in order to inform national public health and health-care policy regarding measures to support children and enhance their mental health.