Mapping of the potential energy surface of the torsions of the phenyl groups of C70Ph8 and C70Ph10 by molecular mechanics reveals the existence of two conformers for each molecule. Energetically, both pairs are quasi- degenerate and therefore they could be experimentally detectable despite the low activation barriers for the inter-conversion (2.4 kcal mol(-1) for C70Ph8 and 3.9 kcal mol(-1) for C70Ph10, respectively). In an effort to pin down the existence of the conformers, the laser induced luminescence spectra of C70Ph8 and C70Ph10 were recorded in several solid solutions. The spectral features for C70Ph8 are rather independent of the nature of the environment and closely resemble those observed before in liquid solution with two main bands separated by more than 2000 cm(-1). For C70Ph10, two new low-energy bands appear which were previously undetected in the liquid phase studies and which depend on the matrix. It is proposed that the doublet bands are fingerprints of the presence of the conformers.