The aim of the study was to compare the pollen season of ash in Bialystok, Bydgoszcz, Cracow, Drawsko Pomorskie, Lublin, Olsztyn, Sosnowiec, Szczecin, Warsaw, Wroclaw and Zielona Gora in 2017 year. Measurements of pollen concentration were performed by the use of volumetric method (Burkard or Lanzoni pollen sampler). The pollen season of ash started in all measurement sites in the last week of March and first week of April. The peak values of seasonal pollen count occurred between 31st March and 10th April in all cities. The highest concentration of 772 pollen grains × m-3 was noted in Cracow, and the lowest of 45 pollen grains × m-3 in Bialystok. The risk of pollen allergy because of the presence in the air the high concentrations of ash pollen grains was the biggest in Cracow (10 days) and in Zielona Gora (9 days). The highest annual sum (SPI, Seasonal Pollen Index) of ash pollen grains was recorded in Cracow (1928), and it was over 9 times higher than in Bialystok (218).