We estimate trends and geographical differences in the heroin epidemic in the European Union plus Croatia and Turkey by analyzing aggregated data on first heroin treatment admissions (cases) during 2000–2009. In 2005–2009 the proportion of drug injectors was higher in Central and Eastern European countries (CEECs) than in Western European countries (WECs), whereas the opposite occurred with mean age at first heroin use and first treatment. During this period, the number of cases, cases per center, and proportion of injectors in WECs declined, whereas mean age at first treatment and first heroin use increased. The opposite occurred in Turkey, except for proportion of injectors, while trends were less clear in the other CEECs. In the 7 WECs with data, trends in 2000–2005 and 2005–2009 were similar. This suggests that the number of recent-onset heroin users and heroin injectors may have declined some years before the study period, especially in WECs.