Examined how interpersonal traits influence psychotherapy success in posttraumatic stress disorder. Interpersonal circumplex data were assessed with the Inventory of Interpersonal Problems (IIP) in a randomized study with 138 patients (mean age 36 years) suffering from posttraumatic stress disorder after trauma in adulthood. Measures included the Impact of Event Scale-Revised (IES-R), the Posttraumatic Diagnostic Scale (PDS), and the Brief Symptom Inventory (BSI). The study compared cognitive processing therapy and dialogical exposure therapy, a Gestalt-based intervention. The interpersonally heterogeneous sample was divided according to the quadrants of the interpersonal circumplex. Results showed that the division into quadrants yielded subgroups that did not differ in their general psychological distress, but the cold-submissive quadrant tended to exhibit higher posttraumatic stress disorder symptom severity and interpersonal distress than the other three. There was also a trend for patients in different quadrants to be affected differently by the treatments. Correlation analyses supported these results. In cognitive processing therapy, more dominant patients had more successful therapies, while in dialogical exposure therapy, success was not correlated with interpersonal style. Results indicate that patients with cold interpersonal styles in particular profited differentially from the two treatments offered. Dividing samples according to the interpersonal circumplex quadrants is considered a promising approach.