The study describes an application of the Inter-Session-Questionnaire (ISF) related to inpatient group psychotherapy. The instrument should be tested with the extension of differentiating intersession experiences related to the person of the therapist as well as the group. In a cross sectional study performed in 13 different hospitals, 702 patients were assessed. These patients were treated in rehab hospitals, acute hospitals as well as special hospitals providing treatment for eating disorders. The sample should be relatively representative for psychosomatic and psychotherapeutic hospitals in Germany. Besides the type of the hospital, we also analysed the influence of group characteristics (size of group, type of group and number of completed sessions) as well as the patients' sex. Surprisingly, there were almost no marked differences of inter-session-experiences related to the the therapist or the group. The profiles of the item judgements of the ISF were similar to those reported for outpatient and day treatment samples. Inter-session-experiences differed in part according to our expectation depending on the variables mentioned above which suggests to use the ISF in specific studies dealing with the process and outcome of inpatient group psychotherapy as well as the differentiation of relevant subgroups.