The meaning of nodal metastases in well-differentiated thyroid carcinoma is controversial. The Authors analyse the impact of lymphatic spread reviewing 1503 cases of well-differentiated thyroid carcinoma treated at the National Cancer Institute of Rome between 1988 and 2005, in order to detect significant prognostic factors through multivariate analysis. Overall, 462 cases of locally advanced well-differentiated thyroid carcinoma, were considered. A multivariate analysis of a subgroup, comprising 97 N+ consecutive cases of well-differentiated thyroid carcinoma, previously untreated, was performed to study prognostic factors for local (N+) and distant (M+) metastasis in well-differentiated thyroid carcinoma. Of the 97 cases, 88 were submitted to surgery for a large well-differentiated thyroid carcinoma, 9 for occult differentiated thyroid carcinoma. After surgery, 12 patients were lost to follow-up, 8 resulted pathologically negative, therefore only 77 cases of pN1 well-differentiated thyroid carcinoma were studied. Considering all cases of well-differentiated thyroid carcinoma, 10-year-overall survival was 58.7% for locally advanced well-differentiated thyroid carcinoma, compared to 94.8% in low stage cases. Neck dissection, margin infiltration and extra-capsular spread were significant prognostic factors. The Authors present a retrospective study of 77 patients with primary differentiated thyroid carcinoma, submitted to thyroidectomy and neck dissection aimed at analysing distribution of nodal metastases according to Robbins' levels classification and defining their prognostic value. All N1b cases, retrospectively reviewed (n. 77), presented clinical and histological evidence of neck nodes metastases from differentiated thyroid carcinoma; histological reports indicated tumour localisation and topographical distribution of metastases; papillary carcinoma was the most common type (72 cases), followed by follicular carcinoma (5 cases). Surgical treatment always comprised total thyroidectomy and 6(th) level dissection. Overall 52 cases were submitted to monolateral neck dissection, 25 to bilateral neck dissection. Treatment of the lateral neck was postero-lateral neck dissection (n. 53), selective lateral neck dissection (n. 20), modified radical and radical (n. 29). Cervical level IV was the most frequently involved (52%), extra-capsular spread of metastases was identified in 22% of the cases. Statistically significant prognostic factors for distant metastases and recurrence on the neck were follicular carcinoma (p < 0.01) and extra-capsular spread (p < 0.001). Age, pT, sex, number of positive nodal metastases, T-extension and the number of nodal positive levels were not significant. In the Authors' experience, histological grade of differentiation, wide tumour excision and neck dissection, in cases of N1b well-differentiated thyroid carcinoma, without residual disease (R1, R2), in the central and lateral neck, are determinant prognostic factors. Extracapsular spread in particular, was found to be a highly predictive factor either of distant metastasis or regional recurrence.