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 ωk in polarized scattering geometry. The experimental observation is that the frequencies of these modes obey the relationship, ω2k = ω22D + ω21D, where ω2D is the vertical intersubband plasmon frequency and ω1D the lateral confined plasmon frequency. This relationship suggests that the additional modes are combined 2D-1D intersubband excitations of collective charge-density type.