Patients with chronic obstructive pulmonary disease (COPD) have the lower airways colonized with pathogenic bacteria in a stable period of the disease and during exacerbations. The etiology of bacterial exacerbations of COPD depends on the underlying disease, the frequency of exacerbations and antibiotic therapy. Microorganisms can be aspirated off the denture plaque biofilm into the lower respiratory tract and could reduce the patient's immunity and cause pneumonia. COPD patients, who are using acrylic dentures in oral cavity, are exposed to denture stomatitis and oral candidiasis. The aim of this study was to establish the composition of denture plaque biofilm and its impact on the oral mucosa in COPD patients. The study included patients in a stable phase of COPD using removable denture and the control group included healthy wearer's appliances. Examinations concerned the oral mucosal membrane and the hygienic condition of prosthetic restorations. Microbiological examinations were performed by taking a direct swab from the surface of acrylic dentures. Seventeen bacterial and fungal strains were isolated from denture plaque of COPD patients, which could be a reservoir of pathogens in the upper and lower airways. The results showed a greater frequency of prosthetic stomatitis complicated by mucosal infections among COPD patients compared to healthy subjects.