Objectives: To evaluate the diagnostic accuracy of sonography and Fine Needle Aspiration Cytology (FNAC). Methodology: This follow-up study was approved by review board and conducted at Endocrine Clinic and Radiology Department of Imam Reza, Kermanshah. The patients were diagnosed to have thyroid nodule examined by FNA and Sonography suspicious malignant cases underwent surgery. Results were entered in SPSS 11.5 chi-Square and Fisher exact test applied to compare malignant and benign nodule characters. Results: In this study 144 patients were examined and 14 cases (9.7%) had malignant nodule. Most of malignant nodules were single (p=0.001), solid (p < 0.001), hypo-echo (p=0.001), with irregular margins (p < 0.001) and with calcification (p=0.041). There was no significant relationship between malignancy and nodule size of larger than 15 mm (p=0.395). Compared with surgery, FNA sensitivity and specificity were calculated as 92.8% and 100% respectively. Conclusion: Based on the result of this study, thyroid nodule size must not be considered as a criterion for malignancy and thyroid nodules of any size must be suspected as malignant. Important criteria for malignancy include irregular edges, being solid, hypoechogenicity and being a single nodule respectively. Compared with Surgery, FNA Sensitivity and specificity were calculated as 92.8% and 100% respectively.