The aim of the study was to assess the effectiveness of cognitive group therapy compared to a waiting list in a sample of patients with heterogeneous non-psychotic disorders. Participants in this study were referred from either the psychiatric in- or outpatient clinic at the psychiatric university hospital in Trondheim, Norway. The patients were assessed with SCID I and SCID II, and randomized either to cognitive group therapy (n=15) or to a waiting list (n=17). Self-report assessments of symptoms and interpersonal difficulties were administered at the start of therapy, after termination of therapy (8 weeks), and at 6 months and 12 months follow-up. Thirty-two patients completed 8 weeks of therapy. Results showed that an 8-week program of CBGT performed better than the waiting list controls, on symptom relief at post-treatment for all patients. The effects of therapy were still upheld at 6 and 12 months follow-up. Cognitive therapy seems to be useful and effective in a group format in naturalistic clinical settings, with patients suffering from various forms of non-psychotic co-morbid psychiatric disorders.