The study of a criminal personality is a crucial task not only in the scope of criminal psychology of today but also for others: forensic sciences, jurisprudence, sociology, etc. Understanding the criminal personality's characteristics is important for diagnosis, designing of psycho-corrective measures, and development of preventive measures. For psychological research, it is interesting to study the deep aspects of personality, it can help to identify the main causes of what is amenable to external observation: one’s behaviour, emotional reactions. Thus, the purpose of this work is to study the personality structure of people who have committed serious crimes. The theory of G. Ammon serves as the methodological basis. The sample: 30 men convicted of violent crimes (art. 105, art. 111 of the Criminal Code of the Russian Federation: murder and intentional infliction of grievous bodily harm, respectively) and 30 men who did not commit offences. The obtained results indicate that the perpetrators of violent crimes have both external (p=0.000) and internal (p=0.000) person-ality boundaries violated; the research revealed violations in the functioning of the Self-system (reflection of the integrity of the personality, its mental unity).