In the treatment of papillary thyroid carcinoma (PTC), supplementary lymph node dissection (LND) is not well standardized. The purpose of this study was to evaluate the significance of the cervical compartments in the lymphatic spread of PTC and the impact of modified radical neck dissection (MRND) as an additional surgical procedure to thyroid resection. From 1999 to 2002, LND of the central compartment (compartment A) was performed in 39 patients. Among this group, additional MRND of the ipsilateral compartment (compartment B) and the contralateral compartment (compartment C) was performed in 29 and 15 patients respectively, who met the selection criteria. The mean number of nodes resected was 11 (5-22) in compartment A, 23 (8-37) in compartment B, and 22 (10-31) in compartment C. Histopathologic findings revealed node invasion of compartment A in 25 patients (64.1%), of A and B in 20 patients (51,2%) and of A, B, and C in 13 patients (33.3%). From the 25 patients with metastases in compartment A, 80% (20 patients) already had metastases in compartment B and 52% (13 patients) had metastases in all three compartments. All patients free of metastasis (M0) in compartment A were also metastasis free in both lateral compartments. Postoperative whole-body scanning I(131) in M0 patients showed no uptake at all. Mapping of the cervical anatomy in compartments seems to be a useful taxonomy for clarifying the lymphatic spread of PTC. Patients having PTC without metastasis in compartment A are almost certainly disease free at the time of operation. Lymph node metastasis in the central compartment appears to be a valuable indicator of lymphatic invasion of the lateral compartment and a strong indication for performance of a unilateral or bilateral MRND to complete the surgical removal of tumor.