Background: Several studies showed that hemocytometer parameters can increase or decrease in some cancer types and diseases. Objectives: we aimed to determine the relationship between the hemocytometer parameters and thyroid diseases by comparing the hemocytometer parameters that are commonly used in papillary thyroid carcinoma (PTC) and benign multinodular goitre (BMG) patients with the healthy control group. Methods: The study was designed retrospectively. The patients who participated in study were divided into 3 groups. Group 1 was determined as BMG group, Group 2 as PTC group and Group 3 as control group. The comparisons were made among the groups in terms of hemocytometer parameters. In the group who were diagnosed thyroid papillary carcinoma, the relationship between the hemocytometer parameters and the bilateral tumor presence, single-sided multisentrite, and tumor diameter (size) was investigated. Results: RDW, MPV values were found to be significantly lower in the control group in comparison with the other groups (p <0.0001). Plateletcrit was found to be significantly lower in the control group in comparison with the other groups (p = 0.0001). In PTC group, no significant relationship was observed between any of the haematological parameters which was examined in terms of multisentrite, bilateral tumor presence. Conclusions: RDW, MPV, haemoglobin content and plateletcrit were found to be significantly higher in BMG and PTC groups. This increase was not specific for either of the two groups. No significant difference was found between any of the hemocytometer parameters and the multicentricity and bilaterality of PTC. But, a possible correlation was observed between aPTT, haemoglobin content and tumor size.