Background: in Russia, the life expectancy of cystic fibrosis (CF) patients increased by 10 years in 2011–2017 being 55.49 years in 2017. However, the number of patients with the chronic infection caused by non-fermenting gram-negative bacilli (NFGNB), e.g., Burkholderia cepacia, Achromobacter spp. etc., increased as well. Aim: to evaluate the differences in the nutritional and functional status and the severity of mutations in CF patients with chronic Pseudomonas infection or NFGNB infection and to assess the sensitivity of P. aeruginosa to tobramycin in CF patients in the Northwest region of Russia. Patients and Methods: 31 patients with CF aged 18–43 years (18 men and 13 women) were examined. The duration of the study was 12 months. Spirometry, anthropometry, and sputum culture were performed. Results: P. aeruginosa alone was isolated in 18 patients (58%), Achromobacter spp. in 9 patients (29%), and Burkholderia spp. in 4 patients (13%). The patients were divided into two groups, i.e., patients with chronic Pseudomonas infection (group 1, n=18, 10 out of 18 patients with mucoid strains of P. aeruginosa) or chronic NFGNB infection (group 2, n=13). The median age and the mode age were 27 years and 27 years, respectively, in group 1 and 24 years and 22 years, respectively, in group 2. It was demonstrated that CF patients with chronic NFGNB infection are characterized by poorer nutritional status (p<0.05) but similar functional status and the severity of CFTR gene mutation compared to CF patients with chronic Pseudomonas infection. It was also shown that Р. aeruginosa is highly sensitive to tobramycin (94.4%). Conclusions: in CF patients, chronic lower respiratory tract infections with Burkholderia cepacia and Achromobacter spp. account for 41.9% of gram-negative rod infections. Further studies and drug sensitivity monitoring are needed. KEYWORDS: cystic fibrosis, DNA test, chronic infection with Pseudomonas aeruginosa, Burkholderia cepacia, Achromobacter spp, non-fermenting gram-negative bacilli, CFTR mutation, nutritional status, pulmonary function tests, inhaled antibiotic therapy. FOR CITATION: Makhmutova V.R., Gembitskaya T.E., Chermenskiy A.G. et al. Comparative characteristics and clinical presentation of cystic fibrosis in adults with chronic lower respiratory tract infections with Pseudomonas aeruginosa and other non-fermenting gram-negative bacilli. Russian Medical Inquiry. 2020;4(4):186–191. DOI: 10.32364/2587-6821-2020-4-4-186-191.