The most visible manifestation of dementia is the progressive inability to activities of daily living (ADL) and to instrumental activities of daily living (IADL). The comprehensive geriatric assessment (CGA) is the validated and recommended instrument to a correct evaluation and decision making in elderly patients. To judge if the decline in cognitive functions is associated with a worsening in functional, emotional and clinical status measured by CGA, we also compared CGA in the same patients stratified for mild, moderate and severe dementia. From September 2004 to November 2005 we studied 47 institutionalized female patients with Alzheimer's disease (AD) and other types of dementia. Mean age was 83.70+/-0.88 years (range 70-101). Their multidimensional evaluation was performed by the CGA. We evaluated geriatric syndromes (AGS, 2004), polypharmacy, frailty, hemoglobin (Hb), serum creatinine (CR) and white blood cells (WBC). We stratified the population in 3 groups for the mini mental state examination (MMSE): severe (MMSE 0-9; 5 patients), moderate (MMSE 10-29; 23 patients) and mild dementia group (MMSE 20-30; 19 patients), and searched for statistical differences in the parameters of CGA. MMSE was significantly related to dependence in ADL (mean=x=1.85), IADL (x=0.57), cumulative illness rating scale-geriatrics (CIRS-G) (x=9.55), geriatric depression scale (GDS) (x=8.71), geriatric syndromes (x=2.49), Hb, CR, WBC and number of drugs (x=6.51, range 2-15) (p=0.001). MMSE low score was also correlated with a worse mini nutritional assessment (MNA) (x=19.5; p=0.003). Frail patients were 61.7%. We found a statistically significant difference in the prevalence of geriatric syndromes between mild vs. moderate dementia group (p=0.02). Mild vs. moderate group, and moderate vs severe group were significantly different concerning Hb levels (p=0.009 and 0.002, respectively). Patients with severe cognitive impairment are more likely to be dependent at ADL and IADL; to present a larger number of comorbidity and geriatric syndromes; to have lower !evels of Hb and higher levels of CR; to be in a worse nutritional status and to take a larger number of drugs. Polypharmacy maybe related to high comorbidity but the risk of irrational drug use should be evaluated. We suggest single testing with CGA as an effective tool providing a comprehensive assessment of elderly, and able to detect unaddressed corrigible problems.