In this paper, hollow and porous Cu2O nanoparticles were prepared by adjusting the cationic surfactant cetyltrimethylammonium (CTAB) concentration in the solution-phase reaction. Structural investigations reveal that Cu2O nanoparticles can be either well-defined hollow nanoboxes or porous nanocubes depending on the synthesis conditions. The transmission electron microscopy (TEM) observations demonstrated that the nanoparticles in general are composed of small grains coherently growing along certain preferred orientations.