We have examined the kinetics of carrier relaxation in three‐dimensionally confined GaAs/AlGaAs layers obtained by growth on prepatterned GaAs(001) with time‐resolved cathodoluminescence (CL). Time‐delayed CL spectra at 87 K reveal that (i) relaxation of hot carriers into the largest 3D confined regions occurs on a time scale of a few hundred ps during the onset of luminescence, and (ii) the luminescence decay time also increases for these larger confined regions, owing to thermal reemission from QWs, diffusion across AlxGa1−xAs barriers, and carrier feeding from surrounding thinner QWs. ©1996 American Institute of Physics.