The catalytic deposition of nanostructured carbons using nickel, cobalt and iron catalysts, supported on 3-dimensional carbon fibre supports, has been investigated and the effects of temperature, gas composition and deposition time on the catalytic behaviour was studied. Samples were characterised using XRD, SEM, polarised light microscopy, TEM, TGA, digital photography and weight change measurements. It was found that the majority of the carbon deposition took place in the first three hours of deposition, with extended deposition times only yielding small increases in the overall rate of carbon deposition. The type of carbon deposited varied from filamentous carbon i.e. carbon nanotubes, nanofibres and microcoils, to encapsulation. It was found that nickel catalysts could be used within larger carbon fibre preforms to catalytically deposit carbon at lower temperatures than those used in industry for the manufacture of pyrolytically densified carbon-carbon composites (> 1000°C).