Cognitive impairment is found in up to 70% of patients with multiple sclerosis (MS). Once thought of as a variant of subcortical dementia with a characteristic set of deficits, we now know that MS-related cognitive impairment can have many faces. This conceptual change in neuropsychology is embedded in a paradigm shift in the neuroscientific understanding of MS over the past 25 years: Partly based on modern neuroimaging techniques, the classical view of MS as an inflammatory demyelinating disease affecting the white matter of the central nervous system has been extended. In particular, many studies have shown that the MS pathology also includes neurodegeneration, and that gray matter structures such as the cerebral cortex can also show focal lesions, atrophy, or both. The authors present an updated summary of the clinical manifestation and neuroimaging correlates of cognitive impairment in MS, and discuss the relatively few treatment options available to date.