  We present results on the X-ray properties of clusters and groups of
galaxies, extracted from a large hydrodynamical simulation. We used the GADGET
code to simulate a LambdaCDM model within a box of 192 Mpc/h on a side, with
480^3 dark matter particles and as many gas particles. The simulation includes
radiative cooling, star formation and supernova feedback. The simulated M-T
relation is consistent with observations once we mimic the procedure for mass
estimates applied to real clusters. Also, with the adopted choices of
Omega_m=0.3 and sigma_8=0.8 the resulting XTF agrees with observational
determinations. The L-T relation also agrees with observations for clusters
with T>2 keV, with no change of slope at the scale of groups. The entropy in
central cluster regions is higher than predicted by gravitational heating
alone, the excess being almost the same for clusters and groups. The simulated
clusters appear to have suffered some overcooling, with f*~0.2, thus about
twice as large as the value observed. Interestingly, temperature profiles are
found to steadily increase toward cluster centers. They decrease in the outer
regions, much like observational data do at r>0.2r_vir, while not showing an
isothermal regime followed by a smooth temperature decline in the innermost
regions.
