Background: Limited information exists regarding the associations between impairment, symptoms, helpfulness of treatments, and service needs after initial treatment of children with attention-deficit/hyperactivity disorder (ADHD). Aims: The aims of this study were to examine persistence rates and associations between parent-reported symptoms, impairment, helpfulness of treatments, and service needs in a retrospective follow-up study of children with ADHD. Methods: Parents of 214 children with a mean age of 12.6 years (SD = 2.1) who were diagnosed with ADHD at five child and adolescent mental health clinics (CAMHS) completed questionnaires 1-10 years (mean = 3.7 years, SD = 2.2) after baseline assessment. The response rate was 43.4%. A community comparison group (n = 110) was recruited from the same area. Results: Approximately two-thirds (60.3%) of the sample fulfilled the DSM-IV symptom criteria of ADHD at follow-up, 84.3% were functionally impaired, and most children (84.7%) were on medication. Inattentive and emotional symptoms were the strongest predictors of impairment across impairment areas. Perceived helpfulness of different treatments varied from 71.8-88.7%, and no significant difference was found between the ADHD sub-groups regarding reported helpfulness. ‘Adjustment of the school situation’ was the most frequent service need, and approximately half of the parents reported needs for care co-ordination. Children fulfilling the symptom criteria of the ADHD Combined sub-group were most impaired and had most service needs. Conclusions: At follow-up, children were highly symptomatic and impaired, despite a high rate of persistent medication treatment. The findings underline the need for more tailored treatment and co-ordinated care over time.