The purpose of this study was to investigate attributes of mental representations of therapists by patients with specific personality disorders (PDs), schizotypal (STPD), borderline (BPD), avoidant (AVPD), and obsessive-compulsive (OCPD), and a comparison group with Major Depressive Disorder and no PD (MDD). The Therapist Representation Inventory-II (TRI) measured characteristics of participants' extra-session thoughts about their therapists. Results showed that patients with STPD had the highest level of mental involvement with therapy outside the session, missing their therapists and wishing for friendship, while also feeling aggressive or negative. Patients with BPD exhibited the most difficulty in creating a benign image of the therapist. Variables such as gender, co-occurring Axis I disorders, and amount of individual psychotherapy received were significant covariates for a number of analyses. The importance of understanding the internal dynamics of patients' thoughts about their treatment relationship was underscored.