In this narrative review, we describe a systematic approach to diagnosing anxiety disorders and their severity on the categorical and dimensional level. We cover all stages of clinical assessment including initial evaluation, treatment course, outcome evaluation and follow up. We take the changes in ICD-11 into account, referring particularly to the new diagnostic categories of selective mutism and separation anxiety disorder. In addition, we discuss selected syndromes with specific importance for behavior medicine like iatrophobia, tokophobia or fear of falling. With respect to treatment planning and evaluation, we propose multimodal assessment comprising physiological, emotional, and cognitive indicators of behavior, and also the specific anxious apprehensions typical for each of the anxiety disorders.