PURPOSE: The aim of this study was to evaluate the risk factors for cervical lymph node (LN) metastasis and the clinical role of internal jugular LN (IJLN) sampling in patients with papillary thyroid carcinoma (PTC) and who had a preoperatively undetected cervical LN. METHODS: One-hundred sixty-three patients with PTC (1 cm in diameter) without clinical evidence of cervical LN involvement were entered the study. All patients the received central compartment node dissection (CCND) and IJLN sampling after total thyroidectomy. We retrospectively analyzed the correlation between the metastatic rate of IJLN and the known risk factors for cervical LN metastasis in the PTC patients. The correlation between the status of the central compartment LN and IJLN metastasis was analyzed. RESULTS: The overall metastatic rate of the central compartment LN and the IJLN was 74.8% and 50.3%, respectively. The metastatic rate of the IJLN was significantly associated with the male gender (P=0.046), primary tumor size (>2 cm, P=0.003) and multiplicity (P=0.006) of the PTC. A young patient age, bilaterality and extracapsular invasion did not achieve statistical significance (P>0.05). The presence of central compartment LN metastasis was a statistically significant risk factor for IJLN metastasis, especially when the rate of central compartment LN metastasis was higher than 50% in the individual patients. CONCLUSION: According to our study, male gender, a large tumor size (>2 cm), multiplicity and the presence of central compartment LN metastasis is considered to be important risk factors for IJLN metastasis in PTC patients. IJLN sampling might be proposed as a relevant tool for making the decision to perform lymphadenectomy in PTC patients with a preoperatively undetected cervical LN.