After an introduction about the basic concepts of attachment theory the diagnostic classification systems ICD, DSM and ZERO TO THREE are reviewed for descriptions and diagnosis of attachment disorders. It is demonstrated how over the last few years attachment theory has been partly adopted in those diagnostic systems. In addition different types of clinically relevant attachment disorders are described. The authors argue that it would be necessary to integrate attachment disorders on a broader base into the current diagnostic classification systems. The diagnostic importance of attachment disorders and their impact on the technique of child psychotherapy are finally discussed.