The defect structure of optically degraded ZnCdSe quantum wells was investigated using transmission electron microscopy. The defects were composed of the dislocation dipoles with a Burgers vector of b=−(a/2)[101] inclined at 45° to the (001) plane. The dislocation dipoles consist of two segments aligned along the [11̄0] direction and the [120] direction. The [11̄0] dipole segments lying in the (111̄) plane were developed by the recombination-enhanced dislocation glide process, while the [1̄2̄0] dipole segments lying in the (2̄11) plane were developed by the recombination-enhanced dislocation climb process. Both processes operate simultaneously.