Many children with, or at risk of, ADHD do not receive healthcare services for their difficulties. This longitudinal study investigates barriers to and predictors of specialist health service use. This is a 5-year follow-up study of children who participated in a cluster randomised controlled trial, which investigated school-level interventions (provision of books with evidence-based information and/or feedback of names of children) for children at risk of ADHD. 162 children who had high levels of ADHD symptoms at age 5 (baseline) were followed up at age 10 years. Using baseline data and follow-up information collected from parents and teachers, children who had and had not used specialist health services over the follow-up period were compared and predictors (symptom severity, comorbid problems, parental perception of burden, parental mental health, and socio-demographic factors) of specialist service use investigated. The most common parent-reported barrier reflected lack of information about who could help. Amongst children using specialist health services who met criteria for ADHD at follow-up, 36 % had been prescribed stimulant medication. Specialist health service use was associated with each one-point increase in teacher-rated symptoms at baseline [inattention symptoms (adjusted OR = 1.40; 95 % CI 1.12-1.76) and hyperactivity/impulsivity symptoms (adjusted OR = 1.23; 95 % CI 1.05-1.44)]. Parental mental health problems were also independently associated with service use (for each one-point increase in symptoms, adjusted OR = 1.41; 95 % CI 1.04-1.91). Severity of teacher-rated ADHD symptoms in early school years is a determinant of subsequent service use. Clinicians and teachers should be aware that parental mental health problems are independently associated with service use for children at risk of ADHD.