We have investigated the wave-vector (q) and magnetic-field (B) dependence of plasmons propagating along quantum wires by means of resonant Raman spectroscopy. We observe a mode with a well-pronounced negative B dispersion that arises from the skipping-orbit motion of the individual electrons within the collective excitation. At higher frequencies we find a set of additional modes that represent a superposition of freely propagating oscillations along the wire and confined oscillations perpendicular to the wires. These modes exhibit in a magnetic field a strong interaction with harmonics, n=2,3…, of the cyclotron frequency nωc.