We have studied the influence of geometric confinement imposed oil the supramolecular architecture of a discotic model compound confined to self-ordered nanoporous alumina. We systematically varied the pore diameter and the chemical nature of the pore walls and studied the systems thus obtained by means of wide angle X-ray diffraction and differential scanning calorimetry. A dominant planar core phase was found for high-energy pore walls consisting of alumina, whereas no apparent texture was present in the case of pore walls coated with non-polar poly(p-xylylene). Inside pores of 35 and 180 nm in diameter, pronounced geometric confinement effects and interfacial effects influence the structure formation. Additionally, we performed molecular dynamics simulations using a coarse-grained discotic potential.