Fibromyalgia (FMS) is a form of arthritis characterized by generalized pain and the occurrence of painful areas called “tender points”. Due to the symptoms common with many other diseases, physicians still have considerable difficulties in its diagnosis. Clinical neuropsychology, a section of clinical psychology, is an interdisciplinary science of the neurobiological bases of human functioning in normal and pathological conditions. The subject of neuropsychology is the study of relationships between observable behavior and the structure and functioning of the brain. In this article the authors look at a complex disease which undoubtedly fibromyalgia is, from the perspective of neuropsychology. The structure of the neuropsychological diagnosis is described. Cognitive functions, diagnostic difficulties, characteristic symptoms of fibromyalgia and psychological mechanisms of pathogenesis are discussed.