Rh catalysts supported on two graphite nanofiber structures (herring-bone - GNF-H and platelet - GNF-P) have been synthesized and characterized by XPS and HRTEM. Rh was partly oxidized after storage in air but reduced to Rh by H-2 treatments at 473 K. The graphitic character of GNF-P was closer to that of highly ordered pyrolytic graphite than that of GNF-H. H, treatment hardly affected the properties of the graphite component. HRTEM shows the appropriate graphite structures and Rh crystallites, mainly on the surface of GNF. The catalytic properties in ring opening of methylcyclopentane (MCP) were close to each other, Rh/GNF-P with more ordered graphite structure favoring "ring opening" to C-6 alkanes. The ring opening reaction was "selective", producing more methylpentanes than hexane. This selectivity increased at higher H-2 pressures. As reported earlier, 2-methylpentane was the main source of < C-6 fragments. Considerably less fragments were produced on both Rh/GNF samples than on other Rh catalysts, due, likely, to more surface H on metallic active sites supplied from hydrogen stored by the GNF supports. (c) 2005 Elsevier B.V. All rights reserved.