Patients with borderline personality disorder (BPD) suffer from affective instability, impulsivity, and identity disturbance which particularly manifest in an unstable or insecure self-image. One main problem for studies of core psychopathology in BPD is the complex subject of identity disturbance and self-image. The purpose of this study was to investigate the self-image of BPD patients with a qualitative research approach. Twelve patients with BPD were compared to 12 patients with remitted major depressive disorder (MDD) without personality disorder, using the Structured Interview of Personality Organization (STIPO). The transcribed interviews were analyzed using a combination of content analysis and grounded theory. BPD patients described themselves predominantly as helpful and sensitive; reported typical emotions were sadness, anger, and anxiety. MDD patients on the other hand reported numerous and various characteristics and emotions, including happiness, as well as sadness and anxiety. Other persons were characterized by the BPD group as egoistic and satisfied, while the MDD group described others as being balanced and secretive. BPD patients displayed an altruistic, superficial, and suffering self-image. Aggressive tendencies were only seen in other persons. Our findings support the concept of a self and relationship disturbance in BPD which is highly relevant for psychotherapy treatment.