Introduction: This study examined whether measures of Personality Disorder (PD) from the Diagnostic and Statistical Manual of Mental Disorder IV, psychodynamic character, psychological mindedness, interpersonal patterns and personality traits predicted treatment outcome for PD patients. Method: Consecutive PD patients were randomly assigned to manualized time-limited supportive-expressive psychotherapy (SEP; n = 76) or non-manualized open-ended community delivered psychodynamic treatment (CDPT; n = 80). Significant predictors were tested together in order to examine whether they moderated or predicted the reduction of psychiatric symptoms (Symptom Check List-90). Results: In the entire sample, patients with more severe levels of PD disorderness (number of positive PD criteria) had slower rates of improvement, but patients with more severe levels of vindictiveness (assessed by the Inventory of Interpersonal Problems [IIP]) had higher rates of improvement. High levels of IIP dominance were significantly related to higher rate of improvement in the CDPT treatment compared with SEP. Conclusion: Due to the fact that more severe PD patients had slower rates of improvement, longer treatment may be needed for this population. Specific interpersonal problems may impact whether patients should receive manualized or non-manualized treatment. Copyright © 2007 John Wiley & Sons, Ltd.