Introduction/Aim. Gingivitis is a common occurrence in children and may well be thought as a risk factor for the appearance and progression of the diseases of parodontal tissues. It is thus necessary to react in a timely and adequate fashion to prevent the disease to become serious and produce parodontopathy. The aim of the study was to establish the efficacy of hyaluronic acid in the treatment of chronic gingivitis in children. Methods. The study enrolled 130 children with permanent dentition. All of the examinees were divided into three groups: group I - 50 patients with chronic gingivitis in which only the basic treatment was applied; group II - 50 patients with chronic gingivitis in which hyaluronic acid was applied in addition to basic treatment; group III - 30 examinees with healthy gingiva (control group). Assessment of oral hygiene and status of the gingiva and parodontium was done using the appropriate indexes before and after the treatment. Inflammation of the gingiva was monitored by way of cytomorphometric studies. Results. The pretreatment values of the plaque index (PI) were high: in the group I PI was 1.94; in the group II PI was 1.68. After the treatment, the PI value was reduced to null in both groups (PI = 0). In the group III PI was 0.17. The bleeding index (BI) in the group I was 2.02 before and 0.32 after the treatment; the BI value in the group II was 1.74 before and 0.16 after the treatment. In the group III BI was 0. In the group I, the Community Periodontal Index of Treatment Needs (CPITN) was 1.66 before and 0.32 after the treatment; in the group II, the CPITN value was 1.5 before and 0.24 after the treatment. In the group III, the CPITN value was 0. In the group I, the size of the nuclei of the stratified squamous epithelium of the gingiva was reduced, although not so much as the nuclear size in the group II of examinees. Conclusion. Basic treatment is able to successfully treat chronic gingivitis in children. The use of hyaluronic acid together with the basic treatment can markedly improve the treatment effect.