Objectives: The severity of inflammation occurring during chronic obstructive pulmonary disease (COPD) isclosely associated with oxidative stress. The aim of this study was to investigate the diagnostic value ofThiol/disulphide homeostasis (TDH) and ischemia modified albumin (IMA) levels in evaluating oxidativestress in COPD patients.Methods: This prospective study was performed with COPD patients presenting to the Kırıkkale UniversityHospital and with healthy volunteers. Subjects’ demographic data (age, sex, body mass index, and smokingstatus), native thiol (NT), total thiol (TT), disulphide (Ds), IMA levels and Ds/NT, Ds/TT and NT/TT ratioswere recorded. Statistical analysis was performed with SPSS 21.0 software.Results: One hundred ninety subjects were enrolled in the study, 141 COPD patients and 49 healthy volunteers.No difference was determined between the patient and control groups in terms of age, sex or body mass index.The antioxidant markers; NT and TT levels and NT/TT ratio were significantly lower in the patient groupcompared to the control group (p < 0.001, p < 0.001, and p < 0.003, respectively). The oxidant markers; IMAlevels and Ds/NT and Ds/TT ratios were significantly higher in the patient group (p = 0.006, p = 0.003, and p= 0.003, respectively). Significant negative correlation was determined between antioxidant and oxidantparameters. Sensitivity values were NT: 87.2%, TT: 83.3%, Ds/NT ratio: 68.1%, Ds/TT ratio: 68.1%, and IMA:77.8%.Conclusions: TDH was impaired in favor oxidants in COPD patients. TDH parameters and IMA can be usedto monitor oxidative stress emerging in COPD.