Although Polish migration to Denmark and Sweden in the early 20th century was not very numerous and was limited in time (1890-1929), it is worth a study, because it had a specific and odd characteristic. Labour and seasonal migration dominated totally. Children of peasants left their homes to earn money, which they sent home, and the families could survive and reproduce themselves of part of the Polish peasant class. Most migrants were young women, who came from Galicia and Russian Poland, but also some men came from Russian Poland. In this article, the author criticizes the existing view in Denmark and Sweden that Polish migrants were wage depressors and/or strike breakers. Instead, he argues, that a vast majority of them made a labour reserve. Employers in Denmark and Sweden actively recruited and contracted Polish workers for seasonal work that native workers were not willing or able to perform on offered conditions. The employers sent the Polish workers back home when there was no more demand for their labour during the winter season, and they recruited workers again when extra labour was demanded next spring. Thus, the Polish workers could spend winter time with their families, and Danish and Swedish employers did not have to pay the reproduction cost of its labour reserve, when they could not put the Polish workers to do profitable labour.