We report structural, energy, and some electronic properties of [n,4]-, [n,5]-, and [n,6]silaprismanes (polysilaprismanes): a special type of silicon nanotubes constructed from dehydrogenated molecules of cyclosilanes (silicon rings) Si4-, Si5, and Si6-rings, respectively. For large n, polysilaprismanes can be considered as the analogs of silicon nanotubes with an extremely small cross-section in the form of a regular polygon. Binding energies, interatomic bonds, and the energy gaps between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) have been calculated using density functional theory for the systems up to ten layers. It is found that [n,4]silaprismane is not thermodynamically stable in the bulk limit (n  ), while the [n,5]- and [n,6]silaprismanes conserve their highly strained framework and become more thermodynamically stable as the number of layers n increase. Moreover, the HOMO-LUMO gap analysis reveals that the [n,5]- and [n,6]silaprismanes with the large effective length can be referred to semimetals or even the conductors. So, they can be successfully used unlike the carbon analogs in nanoelectronics as the functional nanowires or the basis for the computational logic elements without any additional doping or applying the mechanical stresses. Thicknesses of silaprismanes are comparable with that of the smallest carbon nanotubes.