  We investigate the large-scale distribution of galaxy clusters taken from
several X-ray catalogs. Different statistics of clustering like the conditional
correlation function (CCF) and the minimal spanning tree (MST) as well as void
statistics were used. Clusters show two distinct regimes of clustering: 1) on
scales of superclusters (~40/h Mpc) the CCF is represented by a power law; 2)
on larger scales a gradual transition to homogeneity (~100/h Mpc) is observed.
We also present the correlation analysis of the galaxy distribution taken from
DR6 SDSS main galaxy database. In case of galaxies the limiting scales of the
different clustering regimes are 1)10-15/h Mpc; 2) 40-50/h Mpc. The differences
in the characteristic scales and scaling exponents of the cluster and galaxy
distribution can be naturally explained within the theory of biased structure
formation. We compared the density contrasts of inhomogeneities in the cluster
and galaxy distributions in the SDSS region. The estimation of the relative
cluster-galaxy bias gives the value b = 5 +/- 2. The distribution of real
clusters is compared to that of simulated (model) clusters (the MareNostrum
Universe simulations). We selected a cluster sample from 500/h Mpc simulation
box with WMAP3 cosmological parameters and sigma_8 = 0.8. We found a general
agreement between the distribution of observed and simulated clusters. The
differences are mainly due to the presences of the Shapley supercluster in the
observed sample. On the basis of SDSS galaxy sample we study properties of the
power law behavior showed by the CCF on small scales. We show that this
phenomenon is quite complex, with significant scatter in scaling properties,
and characterized by a non-trivial dependence on galaxy properties and
environment.
