STUDY DESIGN: This retrograde study was designed to compare the clinical features and postoperative clinical results of diabetic and non-diabetic patients who had undergone decompression and postero-lateral fusion with instrumentation. OBJECTIVE: To determine whether diabetes affected the outcome of surgery and to identify the clinical features associated with a poor outcome. SUMMARY OF BACKGROUND DATA: Symptoms of peripheral angiopathy and neuropathy as long-term complications of diabetes closely mimic those of lumbar stenosis and there may be a risk of inappropriate surgical intervention in patients with both diabetes and spinal stenosis. In the presence of diabetes, a poor surgical outcome might be expected. But only a few literatures have been documented. MATERIALS AND METHODS: We reviewed 21 diabetic(mean age 58.2 years) and 21 non-diabetic patients(mean age 61.3 years) who had undergone decompression and postero-lateral fusion with instrumentation for lumbar spinal stenosis at a mean of 32 months after operation by reviewing the medical records such as clinical symptoms and results of objective examination(including electrophysiologic study). RESULTS: The preoperative symptoms were similar in the two groups except that abrupt onset of symptoms, the presence of night pain and the absence of any posture-related pain relief were recorded only by diabetic patients. The level of decompression, co-morbidity rate, and intra-operative blood loss were similar in two groups, too. Nerve-conduction velocity was lowered in 66.7% of the diabetic and in 25% of the non-diabetic patients. Polyneuropathy, which are highly suspicious of diabetic neuropathy was detected 46.7% in only diabetic group. The long-term result was excellent or good for thirteen(61.9%) of the twenty-one diabetic patients and for nineteen(90.5%) of the twenty-one non-diabetic patients. CONCLUSIONS: Thus diabetic patients who haute spinal stenosis cannot be expected to have same clinical outcome as non-diabetic patients, which is consistent with the general belief of impression. Therefore, the selection of patient according to clinical and electrophysiologic findings would be the most important factor in determining the rate of success of surgical treatment.