95 elderly and senile patients with mild dementia were followed up: 20 patients with Alzheimer's disease, 25 patients with senile dementia of Alzheimer's type (DAT), 25 patients with vascular dementia (VD), 25 patients with combined vascular and Alzheimer's type of dementia (DAT/VD). Follow-up of patients for 1 and 3 years demonstrated that the diagnosis of mild dementia according to CDR and ICD-10 criteria had a differential-diagnostic specificity and reliability. It was also noticed that the nosologic qualification of mild dimentia syndrome was difficult or even impossible in patients with DAT/VD in conditions of a single examination. Only follow-up studies (during 3 years as a rule) may give a chance to define the diagnostic belonging of mild dementia syndrome more precisely.