AimThis was to study children with early detected externalising behaviour problems compared to matched controls regarding oral health, oral health risk behaviour and the parental evaluation of the child’s oral health and dental care.MethodsChildren aged 10–13 years and with externalising behaviour problems, were compared to matched controls. Behavioural characteristics were based on the Strength and Difficulties Questionnaire. The children and their parents completed questionnaires regarding dental fear, tooth brushing, dietary habits and evaluation of oral health and dental care. Data on dental caries risk assessments, caries, behaviour management problems and dental trauma were obtained from dental files.ResultsThere were no differences in caries prevalence in children with early detected externalising behaviour problems, compared to controls. However, the former group consumed more sweet drinks when thirsty and brushed their teeth fewer than twice daily; they also had more dental trauma in both dentitions and a higher risk range for dental fear, compared to controls.ConclusionsThis study points out potential oral health risk factors in children with early-detected externalising behaviour problems. Although no difference in caries prevalence was observed, externalising behaviour may affect oral health. Therefore, dental professionals should support the families and the children to preserve dental health by offering increased prophylactic measures. There were no differences between children with externalising behaviour problems, compared with controls, regarding the parent evaluation of their child’s dental health. However, more parents in the study group evaluated the dental care as poor or not functioning.