Objectives:
The aim of the presented studies was to empirically analyze the relation between the symptoms of personality disorders and the structure of identity-related senses. The analyses were conducted within two models – based on Millon’s theory of personality and DSM-IV personality disorder classification system.

Methods:
In the studies, a total of 197 university students of various majors were included. The authors used Polish version of the Millon Index of Personality Styles that assess personality styles and offers a Clinical Index to evaluate psychological adjustment, and Personality Disorder Types Questionnaire to obtain DSM-IV diagnoses. The intensity of the identity-related senses was measured using the Multidimensional Identity Inventory. Data were tested for normality, and then Student’s t-tests and ANOVA tests were used to compare the structure of identity-related senses in individuals with a healthy personality and disordered personality.

Results:
Within Millon’s model, three different patterns of disordered personality were found, and they all manifested some identity deficits. Most of the personality disorders covered by DSM-IV also significantly differed on the identity dimensions from healthy personality.

Conclusions:
The results show that identity deficits should be considered as an important symptom of personality disorders, regardless of the adopted model of personality. The most disordered identity is observed in individuals falling into the group with odd or eccentric disorders and into the anxious or fearful cluster. The group with dramatic, emotional or erratic disorders is the most heterogeneous in terms of the level of identity disorganization.