Five inpatients with borderline personality disorder (BPD) participated in 6months of three times per week psychodynamic therapy (PDT). Patients completed a measure of psychological distress every week. A total of 127 sessions were audiotaped and coded using the psychotherapy process Q-set (PQS) and correlated with PQS prototypes of five treatment modelsPDT, cognitive-behaviour therapy (CBT), interpersonal therapy, transference focused psychotherapy and dialectical behaviour therapy. Prototypical CBT process was most prevalent in three of the five PDT-labelled treatments. Prototypical PDT process significantly decreased over time in three of the five treatments. Prototypical process correlations with time were inversely proportional to prototypical process correlations with distress levels. In a multiple regression model that included all five prototypical process correlations across these three treatments, CBT and transference focused psychotherapy predicted distress reduction, whereas PDT predicted increases in distress. PQS items most negatively correlated with distress included the therapist's emphasis on feelings, empathic attunement and control over the interaction. Discussion of dreams or fantasies and therapist aloofness were most positively correlated with distress. An effective PDT treatment model for severely disturbed BPD inpatients requires technical flexibility to supplement CBT processes such as control over the interaction that can structure intense interpersonal dysregulation and stabilize distress. Copyright (c) 2013 John Wiley & Sons, Ltd.