Introduction:GOLD define airflow obstruction by fixed ratio (FR), whereas ATS/ERS spirometry guidelines recommend lower limits of normal (LLN) for diagnosing COPD. Aim:To determine if there is a difference between the two diagnostic criteria for respiratory morbidity and exacerbations. Material methods:COPD patients underwent spirometry. Patients with FEV1/FVC<0,70 were classified as FR+; FEV₁/FVC?0,70 and FVC?80%predicted as FR-; FEV₁/FVC <LLN as LLN+; FEV₁/FVC ?LLN and FVC?LLN as LLN-. The study population was grouped as FR-/LLN-, FR+/ LLN+, and FR+/LLN-. Respiratory morbidity and exacerbations were compared between concordant and discordant groups. 2012-GLI norms were used to define LLN. Results:GOLD and GLI-LLN criterion identified 71.6%, 15.8%, 26% and 57.4%, 20.3%, 22.3% as obstructive, restrictive and normal spirometry, respectively. Patients with airflow obstruction according to either FR or LLN had the highest respiratory comorbidity than those who met neither criteria. Compared with FEV₁/FVC?0,70, in patients with FEV₁/FVC<0,70, the age, sex, and smoking-adjusted hazard ratio was 3.7(95%CI:1.7?8,1;p=0.001) for exacerbations. Compared with COPD patients with FEV1/FVC?LLN, those with FEV1/FVC<LLN, the adjusted hazard ratio was 2.3(95%CI:1.4?3.9;p=0.002) for exacerbations. Adjusted HR for exacerbations were 6.2(2.2-17.1), 3.7(1.7-8.1) for FR+/LLN+ and FR+/LLN- groups as compared to FR-/LLN- group. Conclusion: Patients with airflow obstruction according to FR had more respiratory comorbidity and were more likely to exacerbate than those with LLN only. Patients with FR+ but LLN- were also more likely to have exacerbations than those with FR-/LLN-.