The study compares the hornbeam pollen seasons in Bialystok, Bydgoszcz, Drawsko Pomorskie, Zielona Gora, Opole, Sosnowiec, Cracow, Piotrkow Trybunalski, Warsaw, Lublin, Olsztyn and Szczecin in 2018. The investigations were carried out using the volumetric method (Hirst type pollen sampler). Seasonal Pollen Index was estimated as the sum of daily average pollen concentrations in the given season. Pollen season was defined as the period in which 98% of the annual total catch occurred. The pollen season of hornbeam started first in Bialystok, on the April 3rd. At the latest, a pollen season ended in Lublin and Sosnowiec at the beginning of May. However, in most other cities the season lasted till the end of April. The differences of pollen seasons duration were considerable, from 16 to 36 days. The highest airborne concentration of 168 pollen grains/m3 was noted in Lublin on the April 14th. The maximum values of seasonal pollen count occurred between April 12th and 16th. The highest hornbeam pollen allergen hazard occurred in 2018 in Lublin, Warsaw and Piotrkow Trybunalski.