The presence of IL-17-positive cells is observed in a variety of inflammatory associated cancers and IL-17 has been found to be involved in angiogenesis. The aim of this study is to determine the prognostic significance of IL-17 in NSCLC patients and to examine the correlation between IL-17 expression and lymphatic vessel density in NSCLC tissues. The expression of IL-17 was measured by immunohistochemistry in 52 paraffin-embedded tissues with non-small cell lung cancer. The χ2 test was used to analyze the correlation between IL-17 expression and clinical parameters and lymphatic vessel density (LVD). The Kaplan-Meier method, univariate and multivariate regression analysis was used to analyze the correlation between IL-17 expression and overall survival and disease-free survival. High expression of IL-17 was observed in 25 of 52 lung cancer patients and was associated with smoking status, TNM stage, LVD, overall survival and disease-free survival. Univariate and multivariate analysis showed that IL-17 was an independent prognostic factor for overall survival and disease-free survival. Our results indicate that IL-17 may play a role in the metastasis of lung cancer by promoting lymphangiogenesis. IL-17 expression is an independent prognostic factor in both overall and disease-free survival in NSCLC. © 2009 Elsevier Ireland Ltd