The following points should be considered in dealing with dementia occurring in patients with lacunar infarctions. Lacune is a pathological term and its definition rests on its size (from 2 to 15 mm in diameter). However, terms such as lacunar syndromes and lacunar infarctions are currently used in clinical parlance and recent papers. Patients with lacunar infarctions differ from patients with large infarctions, being more often hypertensive, showing a characteristic but not specific clinical syndrome, and disclosing a significantly lower recurrence rate for new episodes and a significantly higher survival rate. Patients with lacunar infarctions develop a state of dementia 5 times as often as the general population and 25 times as often as in the age group of our patients (65-69 years). Leukoaraiosis, significantly related to arterial hypertension, to lacunar infarction, to an extra risk of future stroke, may be considered an increased risk of cerebral vascular lesions possibly leading to dementia. The relationship between vascular lesions and dementia includes: the strategic location of the lesion (thalamus, corticothalamic areas, bilateral lesions); the whole cerebral hypoperfusion apart from the infarcted area, as shown by PET and SPET; remote effects of cerebral infarctions (diaschisis phenomenon); the so-called incomplete infarction; cerebral atrophy and, particularly, the enlargement of cerebral ventricles, significantly higher in patients with lacunes and dementia as compared with patients with lacunes without dementia.(ABSTRACT TRUNCATED AT 250 WORDS)