Ticks parasitizing on dogs belong to mites of the order Ixodida, class Arachnida. In Poland the occurrence of four species has been recorded most frequently: Ixodes ricinus, I. hexagonus, I. crenulatus and Dermacentor reticulatus. Their importance is due to the fact that they are vectors of many dangerous diseases of humans and animals. The subject of the present study were ticks collected from dogs, patients of several veterinary clinics from the urban agglomeration of the city of Olsztyn. Ticks were collected from May to June in eight consecutive years: 2009–2016. The dominant species was I. ricinus (60.14%) in relation to D. reticulatus (39.71%). In two consecutive years, 2011–2012, single females of Rhipicephalus sanguineus were also identified, an exceptional finding of this species in our country. In D. reticulatus, nymphs predominated over females (23.74% vs 16.0%) while in I. ricinus the respective percentage was 29.6% and 30.55%. However, in subsequent years of the study the proportions between nymphs and females varied greatly in both species.