BACKGROUND: Over the past decades the public health relevance of mental health conditions in children and adolescents has been of growing concern. However, so far no detailed epidemiological data has been available for a representative national sample in Germany. OBJECTIVES: The present paper reports prevalence rates of general and specific mental health problems among children and adolescents in Germany and describes the link between symptoms and impairment as well as the treatment situation. METHODS: The mental health module (BELLA study) examines mental health problems in a representative sub-sample of 2,863 families with children aged 7-17 from the National Health Interview and Examination Survey among Children and Adolescents (KiGGS). Mental health problems were determined using the extended version of the strengths and difficulties questionnaire (SDQ). Further standardised screening measures were employed to screen for anxiety disorders (SCARED), conduct disorder (CBCL), attention deficit-/hyperactivity disorder (FBB-HKS, Conners' Scale) and depressive disorders (CES-DC). Furthermore, substance abuse and suicidal tendencies were assessed. Health-related quality of life (HRQoL) and health care use were determined. RESULTS: Overall, 14.5% of the children and adolescents aged 7-17 fulfilled the criteria for at least one specific mental health problem associated with impairment, or had an overall mental health problem indicated by an abnormal SDQ score and present impairment. However, high comorbidity was found in the children concerned. Symptoms of overall mental health problems were present in 8.6% of the children and 6.6% of the adolescents. This number was reduced to prevalence rates of 6.3 and 4.9% when additional impairment was taken as a criterion. Irrespective of the type of disorder, fewer than half of the children affected were reported as receiving treatment. However, for those suffering from mental health problems, large impairments in HRQoL were observed. CONCLUSIONS: The observed prevalence of mental health problems as well as their large impact on well-being and functioning calls for early prevention. This is especially important with regard to the large decrease in HRQoL in the children and adolescents affected.