Background. Polyarteritis nodosa is an acute, subacute or chronic immune complex disease associated with peripheral and visceral artery involvement, predominantly of middle and small sizes, development of destructive-proliferative arteritis and subsequent peripheral and visceral ischaemia.Cases description. The present paper describes two clinical cases of polyarteritis nodosa in patient R., aged 12, and patient A., aged 9, and demonstrates the difficulties of diagnosing the disease in its early stages. Patient R., aged 12, was admitted to the Rheumatology Unit of the Krasnodar Krai Children’s Clinical Hospital with complaints of red, patchy, dense rash on the palms and plantar surface of the feet. The child has been ill since September 2017, and after a history of tonsillitis suffered a fever of 37 °C, pain in the right heel area, nodular thickening on the feet, livedo reticularis, swelling of both hands. The disease had a recurrent course. The boy was treated with prednisolone, mycophenolate mofetil, hydroxychloroquine and three courses of rituximab (April 2018, January 2019, September 2020). Repeated courses of human normal immunoglobulin and alprostadil therapy were carried out. The treatment showed positive dynamics, fever was eliminated, general well-being improved, and acute inflammatory markers in blood became normal. The skin retained minimal manifestation of livedo, nodularities on the feet did not progress in dynamics. Patient A. was admitted to the Rheumatology Unit of the Krasnodar Krai Children’s Clinical Hospital in April 2022 with complaints of weakness, myalgia of the lower extremities and necrosis foci in the left lumbar region. The medical history indicates that in March 2022, the boy, being in good health before, developed a bluish, painful rash on his lower legs after a workout. Skin changes and soreness resolved on their own without treatment. After examination, a diagnosis was made as follows: juvenile polyarteritis nodosa, activity score — 3.Conclusion. The diagnosis of polyarteritis nodosa can be often problematic due to the very character of the disease featured by absence of specific symptoms, by polymorphism of clinical manifestations, and by lack of clear diagnostic and laboratory markers.