Abstract Background This study, conducted in a Finnish city, examined whether decreasing emergency department (ED) services in an overcrowded primary care ED and corresponding direction to office-hours primary care would modify service usage for specific gender, age or diagnosis groups. Methods This was an observational retrospective study carried out by gradually decreasing ED services in primary care. The interventions aimed at decreasing use of EDs were a) application of ABCDE-triage combined with public guidance on the proper use of EDs, b) closure of a minor supplementary ED, and finally, c) application of “reverse triage” with enhanced direction of the public to office-hours services and away from the remaining ED The annual number of visits to office-hours primary care GPs in different gender, age and diagnosis groups (International Classification of Diseases (ICD − 10) were recorded during a 13-year follow-up period. Results The total number of monthly visits to EDs decreased slowly over the whole study period. This decrease was similar in women and men. The decrease was stronger in the youngest age groups (0–19 years). GPs treated decreasing proportions of ICD-10 groups. Recorded infectious diseases (Groups A and J, and especially diagnoses related to infections of respiratory airways) tended to decrease. However, visits due to injuries and symptomatic diagnoses increased. Conclusion Decreasing services in a primary health care ED with the described interventions seemed to reduce the use of services by young people. The three interventions mentioned above had the effect of making the primary care ED under study appear to function more like a standard ED driven by specialized health care.