Abstract Electronic excitations in AlGaAs-GaAs quantum wires have been investigated by means of resonant inelastic light scattering. Besides a rich spectrum of 1D electronic excitations at low frequencies we fin d at higher frequencies transitions in the regime of the original 2D intersubband excitations. Interestingly, we observe not only the original 2D intersubband excitations but additional modes ω k in polarized scattering geometry. The experimental observation is that the frequencies of these modes obey the relationship, ω 2 k = ω 2 2D + ω 2 1D, where ω 2D is the vertical intersubband plasmon frequency and ω 1D the lateral confined plasmon frequency. This relationship suggests that the additional modes are combined 2D-1D intersubband excitations of collective charge-density type.