PURPOSE: The present study seeks to examine gender differences in internalizing and externalizing problems either parent/teacher or self-reported and to investigate the influence of country-level gender gap on children's mental health problems across countries with high and low gender gap across Europe. METHODS: The School Children's Mental Health in Europe (SCMHE) survey collected data on primary school children living in six European countries, using self-reports (SR) from children (Dominic Interactive), as well as combination of parent- and teacherreports (P/T C) (Strengths and Difficulties Questionnaire) to assess internalizing and externalizing mental health problems. The World Economic Forum's (WEF's) Global Gender Gap report's Gender Gap Index (GGI) was used to categorize countries with high and low gender gap. RESULTS: Boys had greater odds of externalizing problems (OR = 2.6 P/T C, 1.95 SR), and lower odds of internalizing problems (OR = 0.85 P/T C, 0.63 SR). The gender gap's association with mental health problems was different depending on the informant used to identify these problems. A small gap was a risk factor based on reports from adults for externalizing (OR = 1.53) and internalizing problems (OR = 1.42) while it was a protective factor for SR internalizing problems (OR = 0.72). For these problems the gender gap impacted boys and girls differently: a small gender gap was protective for boys but not for girls, including when controlling for key confounding variables. CONCLUSIONS: The differential impact of country-level gender gap observed between self-reported and parent- or teacher-reported mental health is complex but nevertheless present trough mechanisms that are worthwhile to study in depth, with a special attention to the informants and the type of problems examined.< Réduire