Background In recent years, microRNAs (miRNAs) have been found to play an essential role in tumor development. In lung tumorigenesis, targets and pathways of miRNAs are being revealed, and further translational research in this field is warranted. MiR-155 is one of the miRNAs most consistently involved in various neoplastic diseases. We aimed to investigate the prognostic impact of the multifunctional miR-155 in non-small cell lung cancer (NSCLC) patients. Methods Tumor tissue samples from 335 resected stage I to IIIA NSCLC patients were obtained and tissue microarrays (TMAs) were constructed with four cores from each tumor specimen. In situ hybridization (ISH) was used to evaluate the expression of miR-155. Results There were 191 squamous cell carcinomas (SCCs), 95 adenocarcinomas (ACs), 31 large cell carcinomas and 18 bronchioalveolar carcinomas. MiR-155 expression did not have a significant prognostic impact in the total cohort (P = 0.43). In ACs, high miR-155 expression tended to a significant negative prognostic effect on survival in univariate analysis (P = 0.086) and was an independent prognostic factor in multivariate analysis (HR 1.87, CI 95% 1.01 - 3.48, P = 0.047). In SCC patients with lymph node metastasis, however, miR-155 had a positive prognostic impact on survival in univariate (P = 0.034) as well as in multivariate (HR 0.45, CI 95% 0.21-0.96, P = 0.039) analysis. Conclusions The prognostic impact of miR-155 depends on histological subtype and nodal status in NSCLC.