INTRODUCTION: Hashimoto’s thyroiditis (HT) is the most common organ-specific autoimmune disease. The aim of our study was to investigate a possible role of chitotriosidase (Chito) activity as a potential marker of inflammation in diagnosis of patients with HT. In addition, we aimed to determine the levels of inflammation markers such as YKL-40, high sensitivity C-reactive protein (hsCRP) and oxidative stress (OS) parameters such as thiobarbituric acid reactive substances (TBARS), catalase (CAT), superoxide dismutase (SOD), GSH-Px to evaluate an association between those inflammatory and OS markers in patients with HT METHODS: 42 patients with HT and 28 control cases were studied. All cases were euthyroid. Chito activity was measured fluorometrically based on Hollak et al’s. method. hsCRP and YKL-40 levels were measured using ELISA. TBARS, SOD, and CAT activities were determined in hemolyzates. GSH-Px activity was determined by a colorimetric assay RESULTS: Higher Chito concentrations were observed in patients with HT compared to the control group (p=0.002). YKL-40 levels were detected higher in HT but it was not statistically significant (p=0.810). Chito levels were positively correlated with age and negatively correlated with SOD (r=0.360, p=0.021; r=-0.368, p=0.018). YKL-40 levels were positively correlated with FT3 and SOD in HT (r=0.324, p=0.037; r=0.312, p=0.044) and negatively correlated with age (r=−0.463, p=0.002). SOD levels were negatively correlated with age and positively correlated with YKL-40 (r=−0.371, p=0.016, r=0.312, p=0.044). DISCUSSION AND CONCLUSION: We revealed that Chito levels were higher among euthyroid HT patients. This result may point out that Chito levels could be used as a potential marker of inflammation in HT.