Cobalt-based catalysts were prepared by a wet impregnation method on carbon nanotubes (CNTs) support and promoted with niobium. Samples were characterized by nitrogen adsorption, TEM, XRD, TPR, TPO and H 2-TPD. Addition of niobium increased the dispersion of cobalt but decreased the catalysts reducibility. Fischer-Tropsch synthesis (FTS) was carried out in a fixed-bed microreactor at 543 K, 1 atm and H 2/CO = 2 for 5 h. Addition of niobium enhanced the C 5+ hydrocarbons selectivity by 39 and reduced methane selectivity by 59. These effects were more pronounced for 0.04Nb/Co/CNTs catalyst, compared with those observed for other niobium compositions. © 2011 CAS/DICP. All rights reserved.