This study evaluated water sorption and solubility of CAD/CAM composite blocks compared to CAD/CAM ceramic after 8 months in water and artificial saliva. Eight types of blocks were tested, including resin-composite, polymer-infiltrated ceramic network, ceramic-filled PEEK, and feldspathic ceramic. Results showed varying sorption and solubility values, with composite blocks proving hydrolytically stable but less so than ceramic blocks. Water sorption in composites depended on the resin matrix and filler weight percentage.