I review electron transport studies on carbon-based molecular devices. Charge transport is investigated in molecular junctions consisting of open and capped metallic carbon nanotubes acting as electrodes which are bridged by a molecular group. In the second part of the talk, some recent research on spin transport through ferromagnetically contacted double-wall carbon nanotubes will be presented, whereby the giant magnetoresistance (GMR) is the central quantity to be discussed. We mainly focus on the sensitivity of charge and spin transport, as quantified by the linear conductance and the GMR, respectively, to the details of the electrode-molecule interface topology. In the case of spin transport we demonstrate that a simple tight-binding approach may lead to nontrivial behaviour as negative GMR and blocking of transport channels.