In recent years, there has been a significant increase in the number of children with urolithiasis, particularly in the youngest age group. It is estimated that metabolic disorders account for about 75% of cases of stone formation. Urinary tract infections and defects promote stone formation in children. The aim of the study was to evaluate paediatric patients aged up to 3 years, diagnosed with urolithiasis and staying under the care of our Department, with attention being paid to staghorn calculi and the coexistence of urinary tract infections and defects. Material: A total 514 children with urolithiasis, including 122 children aged up to 3 years, were staying under the care of the Department. Methods: We have performed a retrospective analysis of medical records of children hospitalised at the Department of Paediatrics, Paediatric Nephrology and Allergology of the Military Institute of Medicine between 2008 and 2014 due to urolithiasis. Results: Children in the youngest age group, i.e. up to 3 years old, including 50% of children diagnosed in their first year of life, accounted for 25% of patients with urolithiasis. Urinary tract defects and infections coexisted with urolithiasis in more than 70% of the monitored patients. Staghorn urolithiasis was diagnosed in 16.4% of patients, mostly in children with urolithiasis complicated by urinary infection and/or urinary tract defects. Staghorn urolithiasis was not related to urinary tract defects or infections in more than 30% of children.