2-Silapyridine and its divalent silicon isomer 2-silapyridine-2-ylidene have been investigated by ab initio calculations using HF, MP2, and DFT levels and standard 6-31G* and 6-311G(2d) basis sets. It was shown that both molecules are stable minima on the potential energy surface, The silylene ring is more stable by 8.8-11.5 kcal/mol than the silane. The two structures are separated by 56-77 kcal/mol energy barrier (depending on the level of theory). Both the geometry of the rings and isodesmic reaction energies indicate a significant aromatic stabilization. No stable Si=Si bonded dimer of the silylene have been found at the HF/6-31G* level. The head-to tail Si-N bonded dimer was found to be less stable than the two monomers by 18.39 kcal/mol at the HF/6-31G* level. On the basis of the present calculations a substituted 2-silapyridine-2-ylidene is a likely candidate for the synthesis of a new stable silylene.