To investigate the differences in corneal endothelial cell morphology between diabetic patients who were divided by the degree of the severity of diabetic retinopathy and normal patients after phacoemulsification with intraocular lens (IOL) implantation. Department of Ophthalmology, College of Medicine, Pusan National University, Pusan, Korea. Before and 6 months after phacoemulsification, specular microscopy was used to evaluate the number and morphology of endothelial cells in patients with diabetic retinopathy. The patients were divided into 3 groups: group I (n=30 eyes), without diabetes; group II (n=30 eyes), diabetes with severe nonproliferative diabetic retinopathy; group III (n=30 eyes), diabetes with high-risk proliferative diabetic retinopathy (PDR). Postoperative corneal endothelial cell density and hexagonality were significantly decreased and the coefficient of variation in cell size increased in all groups, in contrast to the preoperative state (P<.05). During the postoperative 6 months, the percentage of hexagonal cells showed a tendency to decrease progressively, and this was a significant difference between the 3 groups (P<.05). However, the patterns of change in endothelial cell density and the coefficient of variation in cell size were not different between the groups (P>.05). At the postoperative 6 months, the corneal endothelial cell density and the coefficient of variation in cell size of high-risk PDR patients were statistically changed compared with normal persons (P<.05). However, the percentage of hexagonal cell was not significantly difference between diabetic retinopathy patients and normal patients (P>.05). Corneal endothelial cell density significantly decreased and the coefficient of variation in cell size significantly increased for high-risk PDR patients undergoing phacoemulsification, in contrast to normal persons at the postoperative 6 months.