Objetives: Thisworksaimedtoassesstheclinicaldifferencesbetween Alzheimer’s disease patients with diabetes mellitus and those without diabetes mellitus. Methods: 60 patients with Alzheimer’s disease where divided into two groups; group A having diabetes mellitus and group B without diabetes mellitus, severity of dementia was assessed by the clinical dementia rating scale (CDR), degree of cognitive decline was assessed by global deterioration scale (GDS), behavioral and psychological symptoms were assessed by the neuropsychiatric inventory (NPI) in addition to the minimental state examination (MMSE), vascular complications were excluded using CT brain imaging, diabetic condition was assessed by the blood glucose level. Results: prevalence of severe dementia was significantly higher in AD patients with D.M. than in AD patients without D.M. (43.3% and 16.7% respectively), severe cognitive deterioration was significan tly higher in AD patients with D.M. than in AD patients without D.M. (46.7% and10% respectively), behavioral and psychological symptoms was significantly more prevalent in the first group especially depression, patient with uncontrolled diabetes had more severe dementia than patients with controlled diabetes. Conclusion: diabetes is a risk factor for AD and adds to the severity of dementia inaddition it is associated with more cognitive deterioration, more behavioral and psychological symptoms especially depression even in the absence of vascular complications.