Periapical lesions, as well as periodontal disease, seems to have cyclic patterns of evolution. Periods of burst may be intercalated with periods of quiescence. Because keratinocyte division must occur during cyst growth, it is presumed that epithelium status could indicate the biological activity of radicular cysts (RCs). Th1 and Th2 are important heterogeneous stages of lymphocyte differentiation. Delayed-type hypersensitivity immune reactions are mediated by Th1 lymphocytes, whereas Th2 populations mediate some types of humoral immune response. Th2 lymphocytes are characterized by high expression of CD30 glycoprotein. Th1 and Th2 lymphocytes have not been evaluated in periapical inflammatory lesions. The purpose of this study was to evaluate CD30+ cells in RCs with atrophic and hyperplastic epithelium. A biotin-streptavidin amplified system was used for identification of CD30 receptor. Results demonstrate increased proportions of Th2 cells in cysts with hyperplastic epithelium. Our results suggest that Th2 cells could be associated with RC growth.