The hollow nanoparticles, which contain catalytic species inside the cavity enclosed by a porous nanoshell, are considered an ideal framework for the nanoreactor that efficiently catalyzes the transformation of the selectively transferred substrate molecules with little loss of activity and surface area of entrapped catalysts even in harsh reaction conditions or during the recycling process. In the performance of the hollow nanoreactor, the selectively functionalized interior cavity is the most vital component which allows chemical reactions to occur within the confines of the protected cavity. Therefore, selective and differential functionalization of the internal space of the hollow nanoshell is the important and challenging topic which is demanded for fully exploiting the potential of the hollow nanoparticle in the nanoreactor application. In this context, this review paper intends to make a survey on the synthetic strategies of functionalizing the interior cavity of the hollow nanoparticles and their employment as nanoreator systems which catalyze the chemical reactions and template the growth of nanocrystals. (C) 2014 Elsevier Ltd. All rights reserved.