The paper presents a review of recent results of emission (UV/visible) and absorption (visible and IR) spectroscopical investigations in molecular tube and planar microwave discharges. As a new approach by emission spectroscopy seven band systems of the hydrogen molecule have been analysed to investigate H₂ radiative characteristics and to determine the gas temperature completed by Doppler broadening measurements of H_α, D_α and H₂ spectral lines. H₂ dissociation continuum was used for an estimation of the radiative dissociation rate/degree. By absorption spectroscopy the populations of 4s ArI levels and concentrations of hydrocarbons (e.g. CH₃, C₂H₂, CH₄) were determined. In particular, investigations were focused on spatial distributions of plasma parameters.