Background: Concurrent personality disorder (PD) and substance use disorder (SUD) are common in clinical practice. However, SUD is the main criterion for study exclusion in most psychotherapeutic studies of PD. As a result, data on treatment outcomes in patients with concurrent PD/SUD are scarce. Methods: The study sample consisted of 51 patients diagnosed with severe PD and admitted for psychotherapeutic treatment as a part of routine mental health care. All patients were diagnosed with PD according to the Structured Clinical Interview for PD. Patients were further assessed (DSM-IV diagnostic criteria) to check for the presence of concurrent SUD, with 28 patients diagnosed with both disorders (PD-SUD). These 28 cases were then compared to the 23 patients without SUD (PD-nSUD) in terms of psychiatric hospitalizations and psychiatric emergency room (ER) visits before and during the 6-month therapeutic intervention and every 6 months thereafter for a total of 36 months. Results: The baseline clinical characteristics correspond to a sample of PD patients (78% met DSM-IV criteria for borderline PD) with poor general functioning and a high prevalence of suicide attempts and self-harm behaviors. Altogether, the five outcome variables - the proportion and the number of psychiatric inpatient admissions, the number of days hospitalized, and the proportion and the number of psychiatric ER visits - improved significantly during the treatment period, and this improvement was maintained throughout the follow-up period. Although PD-SUD patients had more psychiatric hospitalizations and ER visits than PD-nSUD patients during follow-up, the differences between these two groups remained stable over the study period indicating that the treatment was equally effective in both groups. Conclusion: Specialized psychotherapy for severe PD can be effectively applied in patients with concurrent PD-SUD under usual practice conditions. These findings suggest that exclusion of patients with dual disorders from specialized treatments is unjustified.