Background The assessment and treatment of patients with a personality disorder have made considerable progress during the last decades. Unfortunately, this progress is often limited to patients with a personality disorder in general. Patients with a personality disorder who also fulfil criteria for a severe mental illness (SMI-PD) profit less. Aim To describe the relationship between contemporary paradigms about personality disorders and the current treatment practices of patients with SMI-PD, and to assess the added value of the recently introduced paradigm epistemic trust and distrust. Method An expert group of mental health professionals, all members of the Expertise Centre for Personality Disorders, conducted a literature study and in addition organized an invitational conference and consensus meetings, resulting in an analysis and recommendations for treatment of patients with SMI-PD. Results The epistemic trust and distrust paradigm clarifies the learning process of patients with SMI-PD and the way patients benefit from treatment. We conclude with elaborations of this paradigm for five contexts of patients with SMI-PD. Conclusion The epistemic trust and distrust paradigm seems a promising concept to improve the often difficult treatment of patients with SMI-PD.