Objective. To improve the diagnosis of acute sinusitis associated with Chlamydia infection in the nasal and sinonasal mucosa of children and its antibacterial treatment regimen. Patients and methods. A total of 168 patients aged 4 to 17 years with acute sinusitis were examined. All the patients underwent verification for two pathogen species: Сhlamydia trachomatis and Chlamydophila pneumoniae. The sample size of children included in a clinical trial was required, as described by A.B. Fainshmidt. Thus, the investigation enrolled a total of 36 children with acute sinusitis, in whom Chlamydia infection had been identified. The patients were divided into 2 groups: a study group and a control group. According to calculations, the representative sample of both groups included 18 people in each (t=1.99). The efficiency of treatment was evaluated in a total group of 28 children; this was due to the fact that 8 children had not undergone a control laboratory test for the pathogen. Nasal mucosal scrape smears were a material for direct identification of chlamydial antigen. For direct detection of chlamydial structures, the investigators used direct immunofluorescence assay and polymerase chain reaction; species-specific antibodies were determined using enzyme immunoassay. Results. Chlamydia infection was identified in 41.7% of the examinees and cyclical polyantibiotic therapy with macrolides proved to be effective in 87.5% of cases. Conclusion. The elaborated set of diagnostic methods contributes to the higher quality of laboratory verification of Chlamydia infection in the upper respiratory tract, determines management tactics for patients with suspected Chlamydia infection, and assists in evaluating the efficiency of therapeutic interventions. The high operational characteristics of the proposed treatment regimen for chlamydial lesions of the paranasal sinuses in children permit the prevention of a chronic inflammatory process and disseminated Chlamydia infection, and cause a reduction in the number of complications, which determines its feasibility in medical practice.