A differentiated diagnostics should not only be conducted at the beginning of psychotherapy but also continuously throughout the process to evaluate the success of the treatment. However, under clinical practice conditions, success monitoring is often carried out hesitantly or not at all. This volume presents various possibilities for therapy-accompanying diagnostics. In addition to general fundamentals and approaches specific to different therapeutic schools, the focus of the book is on diagnostics related to the most important disorder groups: including affective disorders, anxiety disorders, and personality disorders.