NTRODUCTION Chronic obstructive pulmonary disease (COPD) is the most important lung disease lead‑ ing to disability and even death. Recent studies have shown that platelet indices are associated with several cardiovascular diseases; however, data on COPD are scarce. OBJECTIVES We aimed to investigate the relation between the severity of COPD and platelet indices, including the platelet‑to‑lymphocyte ratio (PLR), white blood cell count to mean platelet volume ratio (WMR), and red cell distribution width (RDW). PATIENTS AND METHODS This retrospective study was based on data collected from 153 patients with COPD admitted to our outpatient clinic between March 2014 and March 2015. All participants under‑ went pulmonary function tests, and forced expiratory volume in 1 second, forced vital capacity (FVC), and percentage of FVC expelled in the first second of forced expiration were measured. The population was divided into 4 subgroups according to the severity of COPD: mild, mild to moderate, moderate to severe, and severe. RESULTS We observed a significant increase in platelet distribution width (PDW), mean platelet volume, plateletcrit, PLR, and RDW, and a decrease in WMR with increasing severity of COPD. In a multiple lo‑ gistic regression analysis, PDW and RDW were independently associated with severe COPD. A receiver operating characteristic curve analysis showed that a PDW exceeding 14.85 was associated with severe COPD with a sensitivity of 85% and a specificity of 86%, while an RDW exceeding 14.45 was associated with severe COPD with a sensitivity of 90% and a specificity of 87%. CONCLUSIONS The PDW and RDW are independently associated with disease severity, which may indicate hypoxemia, underlying inflammation, and oxidative stress in COPD.