The normal Raman and surface-enhanced Raman scattering (SERS) spectra of flavanthrone and indanthrone were obtained at several excitation wavelengths. The spectral assignments were aided by density functional calculations. Since both molecules have very high symmetry (C-2h) including a center of inversion, we expect that the modes of u symmetry will be forbidden in the normal Raman spectrum. However, proximity to the surface causes special SERS enhancement of several of the b(u) modes, along with somewhat weaker enhancement of the a(u) and b(g) modes. Copyright (C) 2009 John Wiley & Sons, Ltd.