According to the latest results of Croatian Institute of Public Health, there are more and more children and young adults who are diagnosed with behavioral or mental disorders. Today, personality disorders in adolescence are in the focus, they are important health problem because those problems reflect on families and society in general. Last decades, some important scientific researches on personality disorders in adolescence are present. Adolescence is the period of maturing where the child prepares himself/herself for adulthood; it is the period of turbulence, emotional ambivalences and intensive changes in physical, psychic, emotional, cognitive and sexual development. Numerous risks, to which young people are exposed to, can interfere with normal transition through that period and stimulate occurrence of certain disorder in the mental health of adolescence. Personality disorder is the condition where behavior and experience stand out from habitually and normal behavior; it is not adapted; it interferes with normal functioning of a young adult and it is not justified with the situation where the young person find himself/herself. The cause of disorder is interpreted as the combination of genetic and environmental factors. Risky environmental factors in the childhood take big part in its origin and development of personality disorders. There is a big vigilance in diagnosis of personality disorder in adolescence, because the fact that psychophysical development of a young adult is not finished yet, symptoms of a certain personality disorders must be present for at least one year. We distinguish several types of personality disorders that can be recognized by certain characteristics. Personality disorders are conditions; they are not mental illnesses, but if the symptoms are not recognized on time and the young person does not protect himself/herself from the risky situations and enviornment, peronality disorders can develop in that direction. The key point in the treatment of personality disorders is the early identification of the problem, setting the correct diagnosis and individual approach in choosing of methods of treatment. Psychotherapy is the most common type of treatment, in which cognitive behavioral therapy, dialectical behavioral therapy, psychoanalysis and group psychotherapy are most used. Which one will be used, depends on the assessment that best suits the person with personality disorder. In the program of the mental health protection of the youth, that are introduced on the national level, series of measuers and acitivites are pursued and directed towards the promotion and advancement of mental health, early recognition of difficulties and disorders in mental functioning, and work with high-risk children and youth. The approach is interdisciplinary, teachers and professional associates play the key role in those activities in educational institutions. Their education, consultation and permanent specialization are very important.