In this contribution we provide an overview of our recent work on the mechanical and electronic properties of carbon and boron-nitride (BN) nanotubes, which are of key relevance to practical applications and to our present understanding of low-dimensional structures. On the mechanical properties we look at the nanotube axial stiffness, bending and torsion dynamics. We found that chiral tubes exhibit an interesting asymmetric torsional behaviour with respect to left and right twist that is absent in armchair or zig-zag tubes. Topological defects are seen to modify slightly the mechanical response of the carbon network under applied strain. On the electronic properties we present an analysis of the role of the environment in nanotube density of states relevant for scanning tunneling spectroscopy (STS). Finally we present results on the electronic density of states for BN nanotubes that can be used as a complementary fingerprint of those structures in STS experiments and for their applications in composite (C-BN) electronic devices.