The prognostic value of lymph node metastases in thyroid cancer has been a matter of controversy for many years. However, during the past decade most multivariate analyses have shown a prognostic influence of lymph node metastases in papillary as well as medullary thyroid carcinoma constituting the basis for a standardized concept of lymphadenectomy oriented to the lymph node classification of the UICC (1993). Due to the frequency of lymph node metastases in the ipsilateral cervicocentral compartment (42-86%), in the ipsilateral cervicolateral compartment (32-68%), in the contralateral cervicolateral compartment (12-24%), and in the mediastinal compartment (3-20%), these compartments can be defined as the lymph node regions of the first, second, third and fourth order, respectively. Cervicocentral systematic lymphadenectomy should be part of the en bloc resection of the thyroid gland and the first lymph node region in any thyroid cancer. Cervicolateral as well as mediastinal lymphadenectomy should be performed according to the extent of lymph node involvement, i.e. systematically when multiple lymph node metastases are present, otherwise selectively. One exception is in medullary thyroid carcinoma, where a four-compartment lymphadenectomy is recommended in any patient with positive lymph nodes. Performing a gentle technique using magnifying glasses and bipolar coagulation forceps, systematic lymphadenectomy does not increase the rate of complications, can decrease the recurrence rate and improve survival.