A series of wide-pore (11 nm) SBA-15 mesostructures displaying markedly different morphologies and pore lengths (0.3-5.7 mu m) have been applied as support for 1 wt%Ru-20 wt%Co catalysts. Additionally, a reference catalyst supported on conventional narrow (7 nm)-pore SBA-15 displaying high pore length (6.9 mu m) has also been synthesized. The catalytic supports and metal-loaded catalysts have been characterized by ICP-OES, N-2-physisorption, SEM, TEM, XRD, H-2-chemisorption, H-2-TPR and TPO-MS, and evaluated for the Fischer-Tropsch synthesis (FTS) under realistic conditions (T = 493 K, P = 2.0 MPa, X-CO = 55%). During calcination of catalyst precursors, the deleterious effect of the endo-generated nitrate-derived gaseous oxidants (NO2, N2O) on metal dispersion is diminished in short-pore catalysts due to a shorter pore-residence time, as suggested by TPO-MS. Besides, during H-2 reduction, not only the d(Co3O4) but also the porous structure affects the H-2-TPR profile for the catalysts, suggesting a higher pore-residence time for the formed water leading to a significant metal sintering for long-pore catalysts. Pore length is shown to be more influent than pore diameter (PD = 7-11 nm) on the attained metal dispersion. Due to its effect on metal dispersion, at constant PD = 11 nm, shortening the SBA-15 pores to <= 1.2 mu m leads to 50-67% higher initial FTS Co-time-yields than for catalysts with conventional morphology (pore length >5 mu m). As a result of these higher initial rates, due to a d(Co-0) around the optimal 10 nm, and a lower rate loss during the transitory state (TOS = 0-6 h), short-pore SBA-15 catalysts display very high steady cobalt-time-yields of >250 x 10(-3) mol CO/g(Co) h. Besides, enhanced selectivity toward the desired C5+ hydrocarbons is obtained with short-pore RuCo/SBA-15 catalysts likely due to a lower diffusional barrier for CO to the active sites. (C) 2009 Elsevier B.V. All rights reserved.