Background: White matter lesions (WMLs) are frequent in elderly people, and have been associated with impaired activities of daily living (ADL) and cognitive decline. We sought to examine the role of WMLs and their extent, in regard to basic ADL, instrumental ADL (IADL), and cognitive functions, in a large well-defined cohort examined 3 months after an ischemic stroke. Methods: The study group included 395 of 486 consecutive patients aged 55 to 85 years who, 3 months after an ischemic stroke, completed a neuropsychological test battery and magnetic resonance imaging, and structured medical, neurological, and laboratory evaluations; assessment included an interview with a knowledgeable informant. Results: The patients with the most severe WMLs (n = 213) were older, in comparison with those with moderate (n = 71) or mild/no (n = 111) WMLs. These patients also more often had Diagnostic and Statistical Manual of Mental Disorders, Third Edition dementia; had a lower Mini Mental Status score; were more often women; more often had impaired immediate and delayed memory performance, executive dysfunction, and impaired basic ADL and IADL functions; and had more infarcts and cortical or central atrophy in magnetic resonance imaging. However, there were no significant differences among the 3 groups in stroke severity measured on the Scandinavian Stroke Scale, in stroke-related depression as measured by the Beck Depression Inventory, or in stroke type. According to multiple logistic regression analysis, higher age (odds ratio 1.067, 95% confidence interval 1.036-1.01) and impaired IADL (odds ratio 0.852, 95% confidence interval 0.778-0.931) significantly correlated with severe WMLs. Conclusions: Although the degree of WMLs was not associated with stroke severity, it was associated with global cognitive function, impaired memory functions, executive dysfunction, sex, and impaired basic ADL. Age and IADL functions were independent correlates of severe WMLs.