  We test the imprint of f(R) modified gravity on the halo mass function, using
N-body simulations and a theoretical model developed in (Kopp et al. 2013). We
find a very good agreement between theory and simulations. We extend the
theoretical model to the conditional mass function and apply it to the
prediction of the linear halo bias in f(R) gravity. Using the halo model we
obtain a prediction for the non-linear matter power spectrum accurate to ~10%
at z=0 and up to k=2h/Mpc. We also study halo profiles for the f(R) models and
find a deviation from the standard general relativity result up to 40%,
depending on the halo masses and redshift. This has not been pointed out in
previous analysis. Finally we study the number density and profiles of voids
identified in these f(R) N-body simulations. We underline the effect of the
bias and the sampling to identify voids. We find significant deviation from GR
when measuring the f(R) void profiles with fR0<-10^{-6}.
