This paper aims to investigate the role of the prison institution in protecting the individual from persecutory and depressive anxieties. Authors, in dealing with the discussion on institutional field that is created in the institution prison, emphasize the criterion of isomorphism between service offering and organizational models adopted. The phenomenology of the isomorphism considered from the point of view of the group allows us to observe how the group, compared with some specific images, fantasies and experiences brought by the individual, directly feel such mental events as their own and put in place as a reaction that is defensive and un-conscious.
Keywords: Prison, Isomorphism, Basic assumptions, Field institutional, Group, Mediating object.