In comparison with the large body of evidence on cognitive functioning in adults with multiple sclerosis (MS), there is limited information on cognition in pediatric-onset MS (POMS). Unique vulnerabilities in POMS can derive from having a disease that occurs during key periods of age-expected brain growth, active myelination in the CNS, and maturation of neural networks during the learning curve and key formative years in the academic career of the patient. Therefore, the consequences of MS on developing cognitive faculties can be assessed only in the pediatric population and cannot be simply extrapolated from studies carried on in the adult population. Until the last decade, research in the pediatric population was mainly represented by small clinical series, often limited by the narrow scope of neuropsychological assessment and lack of adequate control groups. Over the last decade, however, cognitive functioning and mood-related difficulties have become an increasing concern as awareness of this population has grown. A few specialized MS centers have begun performing more systematic research in the field in order to assess the prevalence of cognitive impairments and mood-related difficulties in patients with POMS, to better characterize the neuropsychological pattern and determine the functional consequences of these problems. This chapter summarizes our current understanding of cognitive and mood-related difficulties in POMS and highlights perceived gaps in knowledge and priorities for future research.