This work presents systematic studies of the possible classical structures of Si36H36 and C36H36 nanocages using density functional theory calculations. The computed structures, relative stabilities, and electronic properties of these silicon- and carbon-based hydrides are investigated and compared. The results indicate that none of the Si36H36 or C36H36 nanocages exhibit a perfect spherical shape. Hydrogenated nanocages with higher number of adjacent pentagons are more stable and this observation is contrary to the trend of bare fullerenes. The hydrogenated small cages are energetically more favorable than large ones according to the obtained binding energies. Moreover, the energy levels, distributions, and irreducible representations of the frontier orbital for Si36H36 and C36H36 nanocages are also explored. Obvious localizations within the inner space of nanocages are detected for the lowest unoccupied molecular orbital of C36H36. © 2014 Wiley Periodicals, Inc.