The aim of this study was to evaluate whether an insertion/deletion polymorphism (rs3783553) locating in the miR-122 target gene IL1A 3' untranslated region was related to the risk of papillary thyroid carcinoma (PTC). Genomic DNA was extracted from peripheral venous blood of 273 patients with PTC and 509 controls. The IL1A rs3783553 polymorphism was genotyped by using a polymerase chain reaction assay. No significant difference of the distribution of the IL1A rs3783553 polymorphism was observed between PTC patients and controls. However, patients carrying the IL1A rs3783553 ins/ins genotype and ins allele had significantly decreased risks for developing T3 and T4 when compared with patients carrying the IL1A rs3783553 del/del genotype and del allele (ins/ins vs. del/del: OR = 0.22, 95% confidence interval (CI), 0.09-0.54; ins vs. del: OR = 0.58, 95% CI, 0.41-0.83, respectively). These results suggest that the rs3783553 polymorphism may be used as a genetic marker to predict the size/extension of PTC.