Electronic spectra of the S-1<--S-0 transition of the 3,4,9,10-perylenetetracarboxylic-dianhydrid (PTCDA) monomer isolated in superfluid helium nanodroplets have been measured by means of laser-induced fluorescence. The 0(0)(0) transition appears at 20 988 cm(-1) as the dominant line. We obtain clearly resolved the vibrational structure of the molecule. A comparison to Raman spectra of PTCDA films on metallic substrates and PTCDA crystals as well as with calculated frequencies provides the identification of the different modes. The enhanced resolution in the low temperature helium environment and the obtained line positions provide new information about structural properties of perylene derivatives. (C) 2004 American Institute of Physics.