The aim of this work is to propose some thoughts on the construction of alternative realities in which some patients live. They can be designated in various ways as hysterical, borderline, psychotic or even people who manage to lead an apparently normal life. To appear real, alternative worlds must be constructed with special fantasies that do not correspond to the kind of fantasy capable of creating art or myth. The alternative sensorial world is an antagonist of the relational and emotional world and tend to monopolize the interest of the person who builds it. Even when it does not produce serious psychopathological situations, the construction of an alternative reality makes the identity of the person weak and uncertain. These patients prove unable to cope with the difficulties of life and often stop in their emotional growth.