Multiple sclerosis is one of the most common neurological diseases among young people. Treatment and physical therapy are usually focused on motor and sensory deficits experienced by patients. Less attention is paid to cognitive dysfunction, which is very common in this population (30–70% patients). Neuropsychological impairment has a negative effect on numerous aspects of daily living, for instance ability to maintain employment or social life. Cognitive deficits also detrimentally affect functional therapy. Neuropsychological impairment may vary in its severity and type from subtle deficits to dementia. Because of their character and frequent lack of patient’s or caregiver’s complaints, they can remain underestimated or missed during routine neurological examination. Therefore, formal neuropsychological assessment performed with sensitive and reliable methods is required. Patients with cognitive dysfunction should also be provided with neuropsychological therapy. Comprehensive therapy should be aimed at improving motor as well as social and psychological functioning. Hence, it is necessary to include the psychologist in the diagnosis and treatment of multiple sclerosis patients. The psychologist’s presence is important not only to the patient but also to the interdisciplinary treatment team. Information provided by the psychologist helps to assess the patient’s emotional and cognitive functioning, allowing to improve the quality of pharmacological and physical therapy interventions and nursing care.