The unprovoked war of aggression of Russia against Ukraine on 24 February 2022 has generated a historical mass outflow of people fleeing the conflict, unseen in Europe since World War II. While there is a lot of uncertainty regarding the potential length of stay of these refugees in their host countries, many of the working-age adults will seek to work during their stay. This brief reviews the distribution of Ukrainian refugees across European countries and their demographic characteristics. It discusses the existing evidence about the labour market integration of refugees, and applies this information to the case of Ukrainian refugees to provide estimates of the number of active and employed Ukrainian refugees in European countries by the end of 2022 and compares these results to the impact of previous large inflows of refugees, in particular the 2014-17 arrivals.