I discuss the use the weak gravitational lensing effect to study the mass distribution and dynamical state of a sample of 24 X-ray luminous clusters of galaxies. By comparing the mass and light distributions of the clusters it is found that their mass centers, for the majority of the clusters, is consistent with the positions of optical centers. Some clusters present significant mass substructures which generally have optical counterparts. At least in one cluster (Abell 1451), it is detected a mass substructure without an obvious luminous counterpart. Clusters with intra-cluster gas colder than 8 keV show a good agreement between the different mass determinations, but clusters with gas hotter than 8 keV present weak lensing masses smaller than those inferred by the other methods and therefore have been diagnosed to be out of equilibrium.
