Calculations of C-13 nuclear shieldings for low-energy isomers of C36H2x (x = 2, 3) suggest that it should be possible to use experimental C-13 shifts, when these become available, to distinguish the isomeric form of the underlying fullerene cage and, in the case of isomers based on the six-fold symmetrical cylindrical fullerene cage 36:15, the degree of polar hydrogenation. (C) 2002 Elsevier Science B.V. All rights reserved.