Background: Particularly in the last 10 years the conceptual models of partial hospitalization are subjected to major changes, reflecting to the integration of day hospitals in regional mental health service systems and especially to the provision of an alternative to acute inpatient treatment. Systematic nation-wide surveys assessing these changes are missing. Method: After developing a structured questionnaire integrating differences in European mental health care systems, a German national survey of current structural and procedural quality markers of psychiatric day hospitals was carried out in 2001. 51.4% of the addressed psychiatric hospitals (N = 191) returned the questionnaire. Analysis is based on descriptive and correlational methods, compares the situation in the Eastern and Western German Federal States, and uses cluster analysis to differentiate the day hospitals according to their main program function. Results: In general, establishment of day hospitals in Germany has not yet reached the evidence-based capacity level. This statement especially applies to the situation in rural areas. 56% of the day hospitals currently assess themselves as an alternative to inpatient treatment simultaneously providing differentiated psychotherapeutic treatment. Comparing clinical institutions in the Eastern and Western parts of Germany demonstrates the clearer orientation towards acute psychiatric treatment in the recently (mostly after 1995) established East-German hospitals. This is reflected in the spectrum of main clinical diagnoses, in the average length of treatment episodes, in the definitions of contraindications, and in the provided diagnostic measures. While administrative circumstances are homogenous for day hospitals, there is a considerable variation in staff numbers related to the core professions. Conclusions: Guidelines for professional training and continuous qualification as well as staffing have to be modified according to requirements resulting from the change of clinical functions. Each day hospital has to clarify and define its main program function(s), and has to better communicate the consequences for the regional mental health service system.