It was the aim of the study to investigate different factors of group experience in relation to therapy effects and to prove the predictive validity of the Group Experience Questionnaire (GEQ); for this purpose for each scale of the GEQ the values of later "Responders" and "Non Responders" were compared. The sample consisted of 50 patients with psychosomatic diseases who where treated with outpatient integrated psychodynamic group therapy. We found that the GEQ is able to differentiate between successful and less successful patients. Especially the therapeutic factors "autonomy and optimism" as well as "well-being" are of high predictive value. Contrary to former investigations the therapeutic factor "cohesion" was less important, which could hint at the fact that a medium amount of cohesion might be sufficient for an effective process of treatment.