Bottom friction is an important parameter in tsunami inundation and should be included in the numerical simulations in order to reach reliable results. This study shows that smaller friction leads to larger runup values in the simulations and the runup distance of large amplitude waves is more friction sensitive. The analyses are conducted using FLOW 3D, a three-dimensional numerical model efficient in solving free surface flows, and using three experimental benchmark problems, which are commonly used to validate numerical models in coastal engineering.