BACKGROUND: Since the first publication of the psychiatric emergency units (PEUs) in Copenhagen 1985, outpatient facilities have undergone considerable changes. Our aim is to examine how these changes have influenced the activities in the PEUs in the same catchment area. METHODS: We conducted a follow-up study to describe this development in the past 27 years by comparing 1985 variables with same measures in 2012. A random sample of all visits every 10 days in 2012 to three PEUs in Copenhagen were registered and compared with data collected, using the same study design in 1985. MAIN RESULTS: The number of visits has decreased significantly from 367 visits/year/10,000 inhabitants in 1985 to 225 in 2012. Apart from a considerable number (15.6%) of visitors with non-Danish background, the demographic variables have not changed significantly since 1985. Compared with 1985, the diagnostic distribution among the 2012 visitors shows an increased frequency of affective disorders and neurotic and stress disorders, while schizophrenia spectrum and personality disorders show almost the same frequencies in 1985 and 2012. Rates of alcoholism and organic mental disorders show a minor reduction during the 27-year follow-up period. In 1985, 20.7% of the visits ended up without any referrals, compared with 4.8% in 2012. The rate of acute admissions into a psychiatric ward was 60.8% in 2012 compared with 35.65% in 1985. CONCLUSION: The extension of the psychiatric outpatients' facilities since 1985 has reduced the number of visits in the PEUs considerably. The results have shown a change of diagnostic distribution and more severe conditions requiring acute admissions for emergency treatment. Close collaboration with the patients' families, GPs, social authorities and specialized psychiatric outpatient clinics is emphasized.