The aim of our study was to study leukocyte apoptosis and to establish its relationship with changes of cognitive function in patients with chronic brain ischemia (CBI) and hydrocephalus (HC). A comprehensive examination of 110 patients with CBI and HC was performed. Indicators of apoptosis, mitochondrial dysfunction, intracellular oxidative stress were studied by cytofluorimetric method. Significantly higher indicators of ANV+-, PI+-, APK+- and Mito+-cells in the presence of HC. In the group of men, the inverse correlation between the content of AnV+-cells and the result of the MoCA-test — r = –0.42; p = 0.006, in women — r = –0.51; p = 0.005. A significant relationship was found between the content of APK+- and ANV+- cells (r = 0.67, p = 0.003) and between the number of APK+- and PI+-cells (r = 0.73, p = 0.002) in patients aged 60—74. In patients with dementia progression, a moderate relationship was found between the level of cognitive functioning and the proportion of cells in the early stage (ANV+-cells) (r = –0.50; p = 0.026) and late (PI+-cells) (r = –0.30; p = 0.041) apoptosis. In the group of patients with mild and moderate cognitive deficits, correlations between the MoCA scale result and the content of ANV+-cells were recorded at the level of moderate — (r = –0.37; p = 0.040) and PI+-cells at the level of weak (r = –0.24; p = 0.049). Significantly (p < 0.05) higher content of leukocytes in the stage of apoptosis and necrosis and leukocytes with increased content of intracellular APK and with reduced mitochondrial potential compared to patients without HC was found in patients with CBI with HC. There is a significant difference between the values of indicators in middle-aged and elderly patients and indicators of patients older 74 years. The progression of neurological and cognitive deficits was accompanied by an increase of the production of ANV+-, APK+- and Mito+-cells. The highest proportion of ANV+- and PI+-cells was detected in the presence of a combination of dementia, extrapyramidal syndrome and gait apraxia in patients with CBI with HC.