It is important to identify externalizing problem behavior in time to ensure that the consequences can be minimized. Therefore, it is necessary to learn as much as possible about externalizing...Show moreIt is important to identify externalizing problem behavior in time to ensure that the consequences can be minimized. Therefore, it is necessary to learn as much as possible about externalizing problem behavior. This study looks at to what extent parents and teachers report different externalizing problem behavior and whether gender and age of the child can predict this difference. Teachers are expected to report more externalizing problem behavior compared to parents. In addition, it is expected that more externalizing problem behavior will be reported in boys than in girls and that the externalizing behavior decreases as the children get older. 178 participants with an average age of 11 years took part in this study, consisting of 138 boys and 40 girls. Externalizing problem behavior reported by the parents was measured with the Child Behavior Checklist / 6-18 (CBCL) and externalizing problem behavior reported by the teachers was measured with the Teacher's Report Form / 6-18 (TRF). A significant difference was found in reporting externalizing problem behavior between parents and teachers; t (177) = 19.48, p ≤ .001, where teachers reported more externalizing problem behavior. In addition, significantly more externalizing problem behavior was reported in boys than girls (F (1,174) = 6,444, p = 0.012) and no significant difference was found for age (F (1,174) =. 002, p = .966). On average, teachers report more externalizing problem behavior than parents. In addition, it has been found that on average more externalizing problem behavior is reported among boys than among girls and this difference is greater among parents than among teachers. For further research, it is recommended to look at the reason why there is a difference in reports of externalizing problem behavior between parents and teachers.Show less