Background Comprehensive and up-to-date data on child and adolescent health and well-being is essential for monitoring, service development and decision-making. Although nearly all children and adolescents in Finland attend annual health check-ups at child health clinics and school healthcare, the utilization of collected data has been limited. The objective is to produce timely and representative information on the health and well-being of children, adolescents and their families based on routinely collected register data. Methods Data are collected from health check-ups performed at child health clinics and school health care. Recorded data are transferred through patient information systems to the Register of Primary Health Care Visits. The data can be linked to other national registers with personal identity codes. The first phase aimed to evaluate the availability and quality of register-based data through inspection of data coverage on height and weight data of children and adolescents aged 2 to 16 years. Results In 2018, the coverage of height and weight data ranged from 0% to 100% between municipalities depending on age group. Results were published through an interactive map application and municipality-specific summaries by gender and age group at national and municipality levels. The data enabled reporting up-to-date results on the prevalence of child and adolescent overweight and obesity in Finland. Conclusions Data from health check-ups form an excellent database for monitoring child and adolescent health and well-being in Finland. The challenges of utilizing register data are mainly caused by difficulties in data transfer from patient information systems resulting in insufficient data coverage. Publishing local-level reports on data coverage as well as on the results promotes data availability and quality while enabling evaluation of actions needed for promoting the health and welfare of children and their families.