Raman scattering (RS) and Fourier transform–infrared (FT–IR) spectroscopy have been applied to the structural characterisation of manganese dioxides (MDOs). A variety of synthetic battery-grade MDOs are investigated for comparison to the natural phases. The RS and FT–IR spectra are analysed on the basis of the local environment in the MDO structures considering the vibrations of the MnO₆ octahedral building the lattices. The vibrational modes of the MnO₆ units expand over 400–650 cm^−l with additional bands in the low-wavelength region. Structural trends are deduced from the comparison of the vibrational spectra of the MDO phases investigated: birnessite, bixbyite, coronadite, groutite, hausmannite, hollandite, manganosite, pyrolusite, ramsdellite, romanechite, spinel, and todorokite.