ObjectiveMental illness is increasing among young people and likewise the request for health care services. At the same time, somatic comorbidity is common in children and adolescents with psychiatric disorders. There is a lack of studies on health care use in children and adolescents, and the hypothesis was that children and adolescents with psychiatric disorders use more primary‐, and specialized somatic health care compared to children without psychiatric disorders.MethodsIn this retrospective population‐based register study, all individuals aged 3–17 years living in Västra Götaland region in Sweden in 2017 were included (n = 298,877). Linear and Poisson regression were used to compare health care use during 2016–2018 between children with and without psychiatric diagnoses, controlling for age and gender. The results were reported as unstandardised beta coefficient (ß) and adjusted prevalence ratio (aPR) respectively.ResultsHaving a psychiatric diagnosis was associated with more primary care visits (ß 2.35, 95% CI 2.30–2.40). This applied to most diagnoses investigated. Girls had more primary care visits than boys. Likewise, individuals with psychiatric diagnoses had more specialized somatic outpatient care (ß 1.70, 95% CI 1.67–1.73), both planned and unplanned (ß 1.23, 95% CI 1.21–1.25; ß 0.18, 95% CI 0.17–0.19). Somatic inpatient care was more common in those having a psychiatric diagnosis (aPR 1.65, 95% CI 1.58–1.72), with the diagnoses of psychosis and substance use exerting the greatest risk.ConclusionsPsychiatric diagnoses were associated with increased primary‐, somatic outpatient‐ as well as somatic inpatient care. Increased awareness of comorbidity and easy access to relevant health care could be beneficial for patients and caregivers. The results call for a review of current health care systems with distinct division between medical disciplines and levels of health care.