Primary and secondary liver tumors are completely different diseases but are usually treated similarly using high-intensity focused ultrasound (HIFU). However, the acoustic parameters of these tissues are not well documented. In this study, attenuation coefficients were evaluated in fresh primary (N=8) and secondary (N=13) human liver tumor samples recovered by hepatectomy. The average attenuation coefficients of the primary and secondary liver tumors were 0.10 ± 0.03 Np.cm -1 .MHz -1 and 0.20 ± 0.04 Np.cm -1 .MHz -1 , respectively. The average attenuation coefficient of the liver tissue surrounding the primary and secondary tumors was 0.16 ± 0.07 Np.cm -1 .MHz -1 and 0.07 ± 0.02 Np.cm -1 .MHz -1 , respectively. Numerical simulations performed using these values show that completely different HIFU ablation patterns were created in primary and secondary liver tumors using the same exposure parameters. The dimensions of a typical HIFU lesion were two times larger in secondary liver tumors than in primary tumors. HIFU treatment parameters should be set properly according to the acoustic properties of the diseased liver tissue.