BACKROUND: Public health nurses’ experiences of school children’s mental health problems have been studied only a little although the subject is very important and cur-rent. AIM: The aim of this study was to describe the experiences that public health nurses had of school children’s mental health risks, problems and disorders and how they felt their work was appreciated by the parents and the school community. The aim was also to produce information how public health nurses prevented and identified mental health problems and how they worked after the identification. METHOD: This study used qualitative methods for data collection. Five school nurses were interviewed one by one using theme-based interviews. The data were analysed by qualitative theory of normative content analysis. RESULTS: The results showed that most children were fine, but there were some chil-dren who had problems with their mental health. The biggest risks for developing men-tal health problems were problems in the family. The most important ways to prevent mental health problems were talking with the children and reacting if there seemed to be a high risk for problems. The ways to identify mental health problems seemed to be screening, and observing the children’s physical and mental qualities and also asking and talking about their friendships and school work. They could also consult pediatri-cians if they had any worries about mental health issues. If they didn’t know how to proceed with children who had mental health concerns they contacted the child and ado-lescent psychiatry team. The nurses also co-operated with the school doctor, the school psychologist, the school welfare officer, the student social services, the teachers, the clinic, the child welfare and the youth work services during preventing, identification and follow-up treatment. CONCLUSIONS: This study has mainly been made for the school nurses and students. The results can be used to develop preventing and identifying mental health concerns and to plan the follow-up treatment. Public health nurses can also use the results in their mental health work. The study could also benefit all the people who work with children. In the future the study could be done all over Finland.