Background: Children and adolescents who provide care, assistance or support for a chronically ill family member are called young carers. While there is a growing body of research about their specific situation, needs and impact of caring, only very few studies provide information on prevalence rates.; Objectives: The aim was to provide prevalence data for young carers in Germany, and to describe and quantify the nature and extent of their help.; Design: A cross-sectional study.; Settings: Data collection took place between 2016 and 2017 in 44 secondary schools (fifth to 13th grade) in North Rhine-Westphalia, Germany.; Participants: A total of 6313 students aged from 10 to 22 years participated in this study. They represent 0.5% of the basic population.; Methods: Based on the results of a preliminary qualitative study, a standardised electronic questionnaire was developed, which comprised four subject areas: socio-demographic information, general daily aids, health-related quality of life and chronic illness within the family. Statistical analyses included chi-square tests for nominal data and univariate analyses of variance for metrical data together with 95% confidence intervals.; Results: 19.6% (n = 1238) of all respondents state that someone in their family needs help due to a chronic illness. Nevertheless, not all of them are involved in caring activities. The prevalence of those defined as young carers in this study is 6.1% (n = 383), 64% are girls. They take on a wide range of activities. In addition to domestic work, they help their ill relatives with mobility, dressing and undressing, medication, feeding, personal hygiene and with intimate care.; Conclusions: The data provide a good insight into the situation of young carers. The prevalence rate is higher than expected. It refers to the social relevance of this topic and the need for further investigations.