Abstract We present low temperature optical data obtained on narrow quantum wires, fabricated with reactive ion etching and MOCVD overgrowth, in both In 1− x Ga x As/InP and GaAs/Ga 1− x Al x As systems. One-dimensional quantum confinement effects are observed in both cases for the lowest lateral sizes ( L x ), in which carrier lifetimes remain of the order of one nanosecond. For In 1− x Ga x As/InP wires ( L x down to 15 nm, quantum shifts of the photoluminescence peak (up to 30 meV) are observed. For GaAs/Ga 1− x Al x As wires ( L x down to 20 nm). We present photoluminescence excitation spectra showing additional lateral confinement effects, concerning mainly the polarization of the observed transitions.