Hydridosilsesquioxanes SinO3n/2Hn, with n = 4-36, 48, 60, were studied with the semiempirical method MSINDO, a recently presented modification of SINDO1. Within this scheme we calculated the cage structures of these molecules with special focus on the higher homologues in order to present a growth mechanism of insertion reactions. For selected hydridosilsesquioxanes the relative stability of isomers was calculated. Our results allow to draw conclusions about stabilities of the preferred ring sizes as well as the preferred distributions of these rings on the cage surface. The results are discussed in the context of the recently discovered series of higher silsesquioxanes, A comparison is also made with fullerenes. Growth within the homologous hydridosilsesquioxane series by formal insertion of Si2O3H2 units is analyzed and is found to be equivalent to the insertion of even-numbered carbon chains in fullerenes.