We report here the Raman spectrum and lattice dynamics study of a well-crystallized beta-V2O5 material prepared via a high-temperature/high-pressure (HT/HP) route, using alpha-V2O5 as the precursor. Periodic quantum-chemical density functional theory calculations show good agreement with the experimental results and allow one to assign the observed spectral features to specific vibrational modes in the beta-V2O5 polymorph. Key structure-spectrum relationships are extracted from comparative analysis of the vibrational states of the beta-V2O5 and alpha-V2O5 structures, and spectral patterns specific to the basic units of the two V2O5 phases are proposed for the first time. Such results open the way for the use of Raman spectroscopy for the structural characterization of vanadium oxide-based host lattices of interest in the field of lithium batteries and help us to greatly understand the atomistic mechanism involved in the alpha-to-beta phase transition of vanadium pentoxide.