Background: Next to Ixodes ricinus , Dermacentor reticulatus ticks are the most important reservoir and vector of infectious diseases in Europe. In recent years, progressing expansion of D. reticulatus ticks into new territories and an increase in their population size in areas of their previous occurrence have been observed.Methods: The studies on tick population density were conducted in Lublin Province, eastern Poland. The investigated area was divided into 101 equal squares (plots). Additionally, studies on seasonal activity in the preferred habitat of the ornate cow ticks were conducted from 2014 to 2019 in the Polesie National Park.Results: Throughout the study on the tick population density, 19559 adult D. reticulatus specimens were collected. An average density of the ornate cow ticks in Lublin Province was 96.8 specimens/100 m 2 . A significant impact on the tick population density is exerted by meadow areas (Rs=0.281, p=0.0044), while weather conditions have no effect (H=6.08, p=0.1931). The local population of D. reticulatus ticks in the eastern and middle regions of Lublin Province exhibits predominance of spring activity peaks, while autumnal seasonal activity peaks prevail in the rest of the region. Multiannual monitoring of the seasonal activity of D. reticulatus in the Polesie National Park shows the prevalence of autumnal activity peaks in 2014-2019 and spring activity peaks in 2019.Conclusions: The area of Lublin Province is characterized by high density of the ornate cow ticks. Local populations of D. reticulatus show two peaks of seasonal activity. Dynamics of seasonal activity of D. reticulatus is influenced by availability of their hosts. The highest risk of ornate cow tick attacks on animals and humans occurs during spring in the eastern part and in autumn in the western part of Lublin Province.