Memory systems are usually divided in five main categories: semantic, episodic, primary, procedural, and perceptual representation systems. Both semantic and episodic memories are forms of long-term memory with an unlimited capacity. The arterial blood supply of anatomical structures involved in memory comes from different sources. Memory impairment after stroke results from the cumulative effects of stroke and preclinical Alzheimer's disease or to unrecognized preexisting dementia. Mild memory complaints are frequent in stroke survivors. Confusion and memory loss can also result from infarction of the inferior genu of the internal capsule. This syndrome features fluctuating alertness, inattention, memory loss, apathy, abulia, psychomotor retardation, and severe memory loss. Concerning the influence of treatment modalities on memory defects, there are no differences between early and late aneurysmal surgery. Objective memory impairment is more frequent after surgical than after endovascular treatment of the ruptured aneurysm.