Although the relationships between chronic kidney disease (CKD) and cognitive impairment (CI) have been highlighted, the etiology of CI in CKD remains uncertain. Subjects comprised 224 consecutive patients with symptomatic lacunar infarction who underwent magnetic resonance imaging and ambulatory blood pressure monitoring (ABPM). Diurnal blood pressure (BP) patterns were categorized into three groups: dippers, non-dippers and risers. Lacunar infarcts (LIs), including both symptomatic and silent and diffuse white matter lesions (WMLs), were graded into three grades according to their degree. The results of kidney function were evaluated using estimated glomerular filtration rate (eGFR), categorized into three groups: stage 1, 460; stage 2, 30-60; and stage 3, o30 ml min -1 per 1.73 m 2 . There were 44 patients with CI. Confluent WMLs, including WML 2 and WML 3, were found in 36 patients (81.8%), and multiple lacunae including LI 2 and LI 3 were found in 30 patients (68.1%) with CI. Age 475 years (odds ratio (OR), 5.5; Po0.05), male sex (OR, 2.8; Po0.05), non-dippers (OR, 6.3; Po0.05) and risers (OR, 5.6; Po0.05), eGFR 30-60 ml min -1 per 1.73 m 2 (OR, 2.9; Po0.05) and eGFR o30 ml min -1 per 1.73 m 2 (OR, 23.8; Po0.01), WML grade 2 (OR, 5.1; Po0.01) and WML grade 3 (OR, 45.2; Po0.001) and LI grade 2 (OR, 3.2; Po0.05) and LI grade 3 (OR, 6.4; Po0.05) were independently associated with CI. Age 475 years (OR, 4.1; Po0.05), eGFR 30-60 ml min -1 per 1.73 m 2 (OR, 3.7; Po0.05) and eGFR o30 ml min -1 per 1.73 m 2 (OR, 8.7; Po0.05) were independently associated with WML grade 3. Extensive small vessel diseases, CKD and non-dipping status were independently associated with CI. CKD appears to mainly contribute to vascular CI, whereas possibilities of overlapping with other mechanisms such as degenerative CI cannot be excluded. Strict night time BP control and renoprotective treatment may be warranted to prevent CI.