Psychopathy is a personality disorder defined by a specific set of behaviours and personality traits evaluated as negative and socially harmful. The modern conception of Psychopathy was introduced by Clerckley in "Mask of Sanity" (1941), and refined by Hare with the construction of the PCL (1980, 1991), a gold standard instrument for the evaluation of the disorder. Manipulation, deception, grandeur, emotional superficiality, lack of empathy and remorse, impulsive and irresponsible lifestyle, persistent violation of social norms and expectations (Cleckley 1976, Hare 2003) are some behavioural aspects that characterize psychopathic subjects. With this work we intend to study in depth the causes, the traits, in particular the so-called callous-unemotional and risk factors that lead a teenager to become a psychopathic subject. The diagnostic tools useful for the assessment and for the possibilities of intervention that can be put into practice will also be described.