Rationale, aims & objectives: This evaluation was carried out in order to determine the efficacy of the Norfolk and Waveney Adult ADHD Service. With the service not commissioned to offer non-pharmacological support, and with a gap in the research literature, evidence on whether the service model was effective at reducing the impact of ADHD symptoms on service users was needed in order to justify longer term commissioning. Method: Case notes of 113 individuals going through their medication titration process were observed. Scores from the Weiss Functional Impairment Rating Scale (WFIRS), which was routinely collected in the service pre- and post- titration onto ADHD medication, were recorded for comparison. Results: A T test revealed significant improvements in functioning across all domains of the WFIRS after successful titration onto ADHD medication. However, 19.5% of the sample disengaged from the service prior to completing titration. A further 12.5% of the sample did not complete titration due to various factors discussed. Conclusion: While medication has been shown to be effective at improving impairment of functioning in adults with ADHD, high levels of disengagement suggest that more needs to be offered to this population.