A large set of TREESPH simulations is used to test the global morphology of galaxy clusters and its evolution against X–ray data .
A powerful method to investigate substructures in galaxy clusters are the power ratios introduced by Buote \& Tsai .
We consider three flat cosmological models : CDM , \Lambda CDM ( \Omega _ { \Lambda } = 0.7 ) and CHDM ( \Omega _ { h } = 0.2 , 1 massive \nu ) , all normalized so to fit the observed number of clusters .
For each model we built 40 clusters , using a TREESPH code , and performed a statistical comparison with a data sample including nearby clusters observed with ROSAT PSPC instrument .
The comparison disfavors the \Lambda CDM model , as clusters appear too relaxed , while CDM and CHDM clusters , in which a higher degree of complexity occurs , seem to be closer to observations .
A better fit of data can be expected for some different DM mix .
If DM distributions are used instead of baryons , we find substructures more pronounced than in gas and models have a different score .
Using hydrodynamical simulations is therefore essential to our aims .