Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease that can affect cognitive and emotional functioning. About 50% of MS patients present some degree of neuropsychological impairment. Due to its onset in young adulthood (a period of life in which the individual is professionally and socially very active) the presence of cognitive impairment may greatly alter the patient's daily living activities and future life plans. Memory, attention, executive function and information processing speed are the most commonly reported impaired aspects of cognition. Depression, euphoria, and pathological laughing and crying are frequent psychiatric findings. In this paper we describe the distinctive features of cognitive and psychopathological impairments and their relationship to certain disease variables such as illness duration, lesion sites, physical impairment and clinical course. We also deal with aspects of the neuropsychological and psychiatric assessment, emphasizing its importance when psychological counseling or an eventual cognitive training are needed.