Aim: The differential diagnosis of benign and malignant diseases of the thyroid is important in borderline malignancies and malignancies that have not been diagnosed with biopsy. This study aimed to determine endocan molecule levels in patients with thyroid cancer, nodular goiter and thyroiditis. Thus, it was aimed to determine the availability of the endocan molecule in the differential diagnosis of thyroid diseases. Material and Method: The study was conducted between March 1, 2018 and August 1, 2018. During this period, patients who were scheduled for surgery due to thyroid disease and wanted to participate in the study voluntarily were included in the study. A prospective, cross-sectional clinical trial was designed. Patients included in the study were divided into four groups, according to their pathology report results; Group 1: Papillary thyroid cancer (PTC), Group 2: Multinodular goiter on thyroiditis background, Group 3: Multinodular goiter (MNG), Group 4: Follicular thyroid cancer (FTC). Results: A total of 72 patients were included in the study. Multiple analysis comparing the four groups, showed no statistically significant difference between the groups (p>0.050). When the benign and malignant patient groups were compared, endocan levels were found to be statistically significantly higher in the malignant group (p=0.0375). When thyroid carcinoma groups were compared among themselves, the endocan level was detected to be higher in FTC, compared to PTC (p=0.047). Conclusion: The level of "endocan" was observed to increase in malignant thyroid diseases. This was particularly so in FTC, which shows spreading via the hematogenous route. This is an encouraging sign that the "endocan" molecule can be used as a general tumor marker. However, prospective additional studies with large randomized series are needed.