It is well known that nanocrystals exhibit great instabilities associated with their high surface energy. In this concern, nanocrystals grown inside the cavities of a porous host become an attractive integrated chemical system (ICS) because certain processes can be performed in a restricted environment where porous act as nanoreactors. In this work we report the synthesis and characterization of nanosized semiconductors SnO2 and CdS dispersed in porous monoliths. The former was obtained dispersed in porous Vycor glass (PVG) and alpha-NbPO5 glass-ceramic, and the latter in PVG. It was observed that the semiconductor crystallites incorporated in porous monoliths are smaller than those obtained for free precursors decompositions. (c) 2005 Elsevier B.V. All rights reserved.