Identity disturbance is one of the DSM- IV criteria for borderline personality disorder, but there has been little attention to its nature. Four subset of identity disturbance (role absorption, painful incoherence, inconsistency, lack of commitment) have been assessed.

Assess the role of these subsets in patients with borderline personality disorder and examine the relation between identity disturbances with substance- dependency.

This case- control study was conducted on 40 patients with borderline personality disorder referring to Beheshti Hospital in Kerman during 2007-2008; and 40 healthy people who were matched with case group in term of gender, and educational level. Data gathering was done with three questionnaire including a demographic- related questionnaire, disturbance questionnaire (included 35 items), and a questionnaire related to substance- dependency and its related factors. Data analysis was performed using SPSS software (version 11) by mean calculation and t-test and ANOVA.

Mean score of 33 items of identity disturbance questionnaire were greater with significant difference in case group (p < 0.05). Means differences in two groups in all subsets were statistically significant except for role absorption (p < 0.05). Means differences in all subsets in substance- dependent subjects and substance- independent people in both groups were not statistically significant.

Identity disturbance is one of the major criteria for borderline personality disorder, but in different societies the role of its subsets are different. Assessing subsets of identity disturbance has no value in assessing substance- dependency in patients with borderline personality disorder.