Background: Whether CD8(+) IL-17-producing T cells, namely Tc17 cells, play a role in asthma has not been determined. The aim of this study was to evaluate and compare the frequency of peripheral blood Th17 cells and Tc17 cells in asthmatic patients. In addition, the number, ratio and distribution of Th17 cells and Tc17 cells in the lung tissue and splenocytes of asthmatic mice were also investigated. Methods: Th17 and Tc17 cells in the peripheral blood samples of asthmatic patients and in marine spleens were detected by flow cytometric analysis. Th17 and Tc17 cells in marine lung tissues were detected by double immunofluorescence stain. IL-17A levels in marine bronchoalveolar lavage were detected by ELISA. Results: The result of the flow cytometric analysis showed the percentage of Th17 cells among CD3+ T cell populations in patients with asthma was higher than that in healthy controls (P <0.01), The percentage of Tc17 cells was also higher (P <0.05). The percentages of Th17 and Tc17 cells in asthmatic mice were both much higher than that in control animals (P <0.01). Frozen sections of lung tissue showed that the number of Th17 cells and Tc17 cells in the asthma group were all significantly higher than in the control group (P <0.01). Conclusions: Our findings suggest a functional disequilibrium of Th17 and Tc17 cell subsets in asthma that may contribute to the inflammatory process and provide novel insights into a hypothetical driving role of those cells in disease pathogenesis.