Introduction and objective: Lyme disease is the most common chronic, infectious, multisystem, multiform disease. The region of Warmia and Mazury, as well as Podlasie, and the region of Lower Silesia are endemic areas for Lyme disease in our country. The aim of the study was to analyse the prevalence of Lyme disease among children from the Warmian-Masurian Voivodeship hospitalised in the Provincial Specialist Children’s Hospital in Olsztyn. Materials and methods: The study group consisted of 109 patients admitted to a hospital with Lyme disease diagnosis. The study used a retrospective method based on the analysis of the medical history of patients admitted to the hospital in the period from January 2013 to December 2018. Results: More than half of the cases (56.88%) were elective hospital admissions, while 43.12% were emergency admissions. The largest number of patients complained of headaches (68.81%). In about half of the patients (54.13%), the first symptoms of the disease appeared in less than 3 months. Conclusions: Among hospitalised patients diagnosed with Lyme disease, urban school age girls were significantly more likely to be affected. Most patients hospitalised due to Lyme disease denied a tick bite. The majority of patients hospitalised during the study period presented with non-specific symptoms of Lyme disease. The time between symptom onset and the diagnosis of Lyme disease was significantly shorter in children under 7 years of age. The time of hospitalisation of children under the age of 7 years was significantly shorter than in other age groups.