Attention is focused on polymer modified cementitious systems, and in particular on their interactions with ceramic tiles, having a porous or a compact structure, in different installation conditions. Analytical techniques like XRD, IR spectrometry, TGA, DSC, He porosimetry (BET) and SEM were used. The hardening kinetics (in the early 28 days) were studied, and correlated with the physical-mechanical properties of the adhesive under consideration. The results achieved show that the type of tiles involved (with either high or low water absorption) is the basic parameter, in view of the development of mechanical resistance in adhesives. This effect can be substantially modified through polymers additions.