[en] Aim: To evaluate the association between liver stiffness measured by acoustic radiation force impulse (ARFI) elastometry and the outcome of antiviral treatment in patients with chronic viral hepatitis B and C. Materials and methods: Thirty-eight patients with chronic viral hepatitis B (n = 16) or hepatitis C (n = 22) underwent liver biopsy and ARFI elastometry of the right hepatic lobe. A follow-up assessment using ARFI was performed a mean of 2.3 years after the baseline evaluation. The patients with favourable outcome were classified in group S and those receiving no treatment, showing no response to treatment, or experiencing a relapse were classified in group N. Results: The 38 patients had an initial mean ARFI value of 1.56 ± 0.62 m/s as compared with 1.54 ± 0.64 m/s in the follow-up evaluation. Group S showed a significant decline in ARFI values (1.55 ± 0.60 m/s versus 1.34 ± 0.47 m/s; p < 0.05) and included 16 (64%) patients with lower shear wave velocities at follow-up. In group N, liver stiffness values showed a slight but not significant increase (1.57 ± 0.70 m/s versus 1.93 ± 0.77 m/s). Conclusion: Changes in liver stiffness during antiviral therapy can be assessed by ARFI reflecting response or no response. ARFI elastometry is an additional, useful tool for the follow-up assessment of treatment outcome in patients with chronic viral hepatitis B or C infection