[en] The electronic structure calculations are systematically carried out within the density functional formalism for understanding the structural and electronic properties of a number of selenium nanotubes. In particular, single walled selenium nanotubes (achiral) are studied in this work. Our investigations reveal that the lower diameter nanotubes are unstable. Beyond certain diameter, the tubes retain their tubular structure and they show metallic property. Furthermore, work-functions of these tubes are found to depend on their diameters and differ from that of the bulk selenium surface. - Highlights: • The selenium tubes become stable and retain tubular shape beyond certain diameter. • In contrary to bulk selenium, the tubular structures show metallic property. • The work-functions of tubes vary with diameter. The amount of variation is 1.2 eV.