This guide equips healthcare practitioners with the essential knowledge and structure needed to carry out thorough ADHD assessments in adults. Drawing on the authors' extensive clinical experience and their leadership in ADHD assessment, service development and clinical guideline work, it explains how to evaluate symptoms, functional impairment, and co-occurring conditions with accuracy and confidence. It distils the core principles of effective semi-structured interviewing and demonstrates how tools such as ACE+ can be applied thoughtfully in practice. The book also provides clear guidance on pre-assessment information gathering, differential diagnosis, report writing, and feedback, supporting healthcare practitioners beyond the interview itself. Designed for use across public and private healthcare systems internationally, this clear, practical resource is essential reading for healthcare practitioners involved in adult ADHD assessment.