This insightful book offers professionals a comprehensive guide for navigating the new way of diagnosing and understanding personality difficulties and disorders introduced in the ICD-11. Through in-depth clinical examples, these experienced authors illustrate clearly how to determine severity, specify the five trait domains, and interpret aspects of personality dysfunction, including specific combinations of trait domains. The book also provides guidelines for differential diagnosis in relation to a range of other persistent mental disorders, clinical decision- making, individualized treatment planning, necessary treatment intensity, and psychotherapeutic focus. Readers will appreciate the exploration of available standardized instruments for classification, as well as the guide using the old classifications in the ICD-10 and the DSM-5 with the ICD-11 guidelines in the appendix. This book provides a roadmap for psychologists, psychiatrists, other mental health professionals, and students to use the latest advancements in classification to enhance patient care of people with personality disorders.