Introduction There is a high incidence of Axis II personality disorders (PDs) in patients with bipolar illness, but their influence on the prospectively measured course of bipolar disorder has been less well explicated. Methods 392 outpatients with bipolar disorder gave informed consent, completed the PDQ4 99 item personality disorder rating, and where clinically rated during at least one year of prospective naturalistic treatment. They were classified as Well on admission (N = 64) or Responders (N = 146) or Non-responders (N = 182) to treatment for at least six months. Results Patients who were positive for PDs were very infrequently represented in the category of Well on admission. In addition, patients with borderline, depressive, and schizoid PDs were significantly more likely to be Non-responders compared to Responders upon prospective naturalistic treatment in the network. Conclusions Patients with bipolar disorder and comorbid PDs were in general less likely to be Well from treatment in the community at network entry or to be a Responder to prospective treatment in the network. Therapeutic approaches to patients with PDs deserve specific study in an attempt to achieve a better long-term course of bipolar disorder.