Primary aim of this study was to determine the extent and type of self-reported interpersonal problems in patients with non-affective psychoses and their impact on psychosocial functioning. Furthermore, we aimed to explore potential links with the psychodynamic construct of Stavros Mentzos' "psychotic dilemma", which describes an insufferable inner tension caused by an individual's struggle of being torn between "self-oriented" and "object-oriented" tendencies. In a cross-sectional study among 129 patients with non-affective psychoses, measures of cognition, symptom load and social functioning as well as a tentative, psychodynamic assessment of Mentzos' "dilemma" were obtained during a clinical research visit. Self-report data on interpersonal problems were gathered using the Inventory of Interpersonal Problems (IIP-64D) and compared with a German representative standard sample. Second, IIP-64D scores were compared between groups with or without Mentzos' "dilemma". Hierarchical regression analyses were performed to test for the impact of interpersonal problems on psychosocial functioning, while controlling for cognitive deficits and psychopathology. Results showed that IIP-64D scores differed significantly from healthy controls, except for "self-centred" and "intrusive" interpersonal styles. Participants with a potential "psychotic dilemma" scored significantly higher on the subscales: "domineering", "self-centred", "cold", and "socially avoidant" than the group without a "psychotic dilemma". The total amount of interpersonal problems, and particularly high scores on the IIP-64D "socially avoidant" subscale, predicted psychosocial dysfunction, whereas a "cold" interpersonal style had an opposite effect. In conclusion, specific interpersonal problems may predict psychotherapeutic outcome measures like psychosocial functioning and are partly compatible with the psychodynamic construct of Stavros Mentzos' "psychotic dilemma".