Background/aim: The most common thyroid malignancies are papillary and follicular thyroid carcinomas. They account for approximately 85%-90% of all thyroid cancers. Recent studies have reported the relevance of cyclooxygenase-2 (COX-2) gene polymorphism in human carcinogenesis. The aim of this study was to investigate the relationship between thyroid carcinoma and COX-2 gene polymorphism in the Turkish population.Materials and methods: We included a total of 96 differentiated thyroid cancer patients (mean age: 46.9 ± 10.3 years; 14 males, 82 females) and 83 healthy control subjects (mean age: 46.0 ± 10.6 years; 39 males, 44 females). The frequency of -765G>C, -8473T>C, and 1195A>G gene polymorphisms in the COX-2 promoter region was investigated in thyroid cancer patients and the control group using the high-resolution melting method. Results: COX-2-765G>C and COX-2-1195A>G gene polymorphisms were similar between thyroid cancer patients and the control group. There was a statistically significant difference between COX-2-8473T>C gene polymorphism in the thyroid cancer group and the control group (P = 0.012).Conclusion: The single nucleotide gene polymorphism COX-2-8473T>C might contribute to genetic susceptibility to differentiated thyroid cancer in the Turkish population.