In recent years, acute respiratory viral infections (ARVIs) and other acute respiratory diseases (ARDs) have acquired some new characteristics of the disease course. The structure of complications has changed, in particular, such complications as community-acquired pneumonia (CAP) and lesions to the upper respiratory tract have become significantly more common. CAP remains one of the main causes of death in patients with ARVIs and other acute respiratory infections due to bacterial resistance to antibiotics. Objective. To assess drug sensitivity of Moraxella catarrhalis strains isolated from patients with complicated ARVIs or ARDs. Materials and methods. Drug susceptibility assessment was performed using the disk diffusion method (DDM) and gradient diffusion method (E-test). The production of β-lactamases was evaluated using nitrocephine, a chromogenic substrate. Results. Isolated strains of M. catarrhalis were resistant to third-generation cephalosporins and sensitive to fourth-and fifth-generation cephalosporins. More than 70% of M. catarrhalis strains developed resistance to macrolides; 8% of strains were resistant to amoxiclav. All isolated M. catarrhalis strains were sensitive to respiratory fluoroquinolones, carbapenems, and ampicillin-sulbactam. © 2021, Dynasty Publishing House. All rights reserved.