This aim of this study was to assess the potential role of IL-33 in the pathogenic process of chronic hepatitis B (CHB). The levels of serum IL-33 and soluble ST2 (sST2) in CHB patients and healthy controls (HC) were determined using enzyme-linked-immunosorbent serologic assay, and the Th1 (IFN-γ, TNF-α, IL-2) and Th2 (IL-4, IL-6, IL-10) cytokines by cytometric bead array. It was found that the levels of serum IL-33 in CHB patients were significantly higher than that of HC at the base line, but decreased after treatment with adefovir dipivoxil for 12 weeks. The levels of serum sST2, as a decoy receptor of IL-33, were significantly higher in CHB patients than the HC. There was no correlation between the levels of serum sST2 and IL-33. The concentrations of serum Th1 (IFN-γ, IL-2) and Th2 (IL-6, IL-10) cytokines in CHB patients significantly increased after treatment compared to the baseline. These results suggest that IL-33 is involved in the pathogenesis of CHB and that adefovir dipivoxil therapy can attenuate the production of IL-33 in patients with CHB.