This book provides a comprehensive, state of the art overview that covers both the diagnosis and the treatment of dual disorders – joint psychiatric and substance use disorders associated with a worse outcome and disease progression than single psychiatric or addictive disorders. The book is designed to be highly relevant to clinical work and the organization of care systems and meets the real need for a European perspective on dual disorders that takes into account the realities of European treatment organization. All chapters have been written by European authors on the basis of existing European treatment programs or guidelines and European research. The book will be invaluable for all health professionals working in mental health and addiction care, who are increasingly confronted with patients suffering from dual disorders.