Psychiatric symptoms (or mood/emotional disturbances) are diverse in patients with neurological diseases, that include depression, anxiety, emotional incontinence, anger, fatigue, and apathy. These symptoms are common; more than 1/3 of the patients suffer from these symptoms. Unfortunately, they have been neglected because 1) unlike other neurological symptoms such as motor dysfunction, speech disturbances or visual field defect, these symptoms are not visible and difficult to be noticed unless they are specifically examined by a physician who is properly educated on this problem 2) they are often not regarded as neurological symptoms either by the patients or their caregivers 3) they are relatively poorly studied by both neurologists and psychiatrists, and accordingly, are unfamiliar to the physicians. Especially, although `depression' is well known to physicians, other symptoms such as emotional incontinence, anger, fatigue or apathy are not appropriately assessed by physicians, and frequently misdiagnosed as depression. Moreover, there are difficulties in diagnosing depression in patients neurological diseases. For example, the individual items included in depression diagnosis such as sleep disturbances, appetite loss, or fatigue can result from neurological diseases or comorbid physical conditions in patients with neurological diseases. Therefore, a diagnosis of `depression' should be made cautiously. Finally, it should be understood that the importance of different mood/ emotional syndromes differ among various neurological diseases; for instance, although emotional incontinence and anger occur in as many as 20-30 % of stroke patients, apathy and fatigue are more important symptoms than these for patients with neuro-degenerative disease. In clinical practice, recognizing these symptoms is important because they negatively affect the patients' quality of life, impair the functional recovery, increase the mortality, and increase the caregiver burden. Nevertheless, unlike other neurological symptoms such as motor/sensory dysfunction, and speech disturbances, they are relatively well managed mostly by pharmacological therapy such as selective serotonin re-uptake inhibitors (SSRI). The phenomenology of these neuropsychiatric symptoms and related factors, pathophysiological mechanism, and treatment strategies should be properly educated for neurologists, psychiatrists and other physicians. The book is written by experts in this field to disseminate important knowledges to neurologists, psychiatrists, psychologists and other physicians and will eventually benefit patients with neurological diseases.