<p>A large-scale first-principles simulation of the structure and stability of SrTiO₃ single- and double-wall nanotubes with different chiralities has been performed for the first time using the periodic PBE0 LCAO method. The initial structures of nanotubes have been obtained by rolling up slabs consisting of two and four alternating (001) SrO and TiO₂ planes. In the majority of the considered cases the inner or outer TiO₂ shells of 4-layer nanotubes undergo a considerable reconstruction due to shrinkage or stretching of interatomic distances. Double-wall nanotubes constructed from 2-layer single-wall nanotubes with the intertube distance less than 4.5&ndash;5.0 &Aring; merge to stable polyhedron-shaped tubular objects consisting of blocks with a distorted cubic perovskite structure.</p>