The concepts of statistical and clinical significance of pre-post-changes have been used to class patients into four groups of therapy outcome: "recovered", "improved", "unchanged" and "deteriorated". Aim of this study is to investigate the advantages of this classification in comparison to a simple division into "successful" and "not successful". 43 patients were examined before and after an in-patient psychotherapy and again two years later with several test inventories. Therapy outcome was measured by the changes in the Global Severity Index of the SCL-90-R. "Recovered" and "improved" patients did only differ in regard to their initial symptom severity, but not in regard to the amount of symptom reduction or stability of therapy effect. "Deteriorated" patients could reduce their increase in symptoms until follow-up. Our results do not indicate a general advantage of the classification into four outcome groups over a division into "successful" / "not successful".