Objectives In this study, we aimed to compare the adequacy of conventional smear (CS) and liquid-based cytology (LBC) methods in thyroid fine-needle aspiration biopsy (FNAB) samples obtained without an accompanying cytopathologist during the procedure. Furthermore, we aimed to investigate the presence of a significant difference between the rates of nodules classified as Bethesda Category III and malignancy in both techniques and the features of the nodules affecting malignancy. Methods A total of 625 nodules from 572 patients who were found suitable for biopsy were included in this retrospective study. FNABs were performed by interventional radiologists without an accompanying cytopathologist during the procedures. The specimens were either prepared using CS or LBC preparation methods. Cytopathological diagnostic adequacy and cytopathological results of the specimens were evaluated according to Bethesda category, and the relationship between the morphological findings was evaluated retrospectively. Results Of all the biopsy preparations, 338 (54.1%) of them were transferred to pathology in liquid-based solution and 287 (45.9%) were transferred as CS. Malignancy rates of the biopsy samples were found similar in both LBC and CS methods. Considering the nodules classified as Bethesda Category II, III, IV, V, and VI, there was no statistical difference between the results of both methods. Non-diagnostic biopsy rate was higher in the specimens prepared by CS method (p<0.001). Conclusion In this study, the adequacy rate of FNAB was found significantly higher in LBC method compared to the CS method. LBC was more practical and faster than the CS method. We think that LBC method may be preferred in FNAB of thyroid nodules.