We report on a 13-year-old girl with late infantile neuronal ceroid lipofuscinosis (NCL) in whom PET scanning with [18F]-2-fluoro-2-deoxy-D-glucose ([18F]/FDG) was performed. Early psychomotor development was normal. At the age of 2 years, neurological signs such as hypotonia and incoordination appeared, followed by visual failure and ataxia. At the age of 4, funduscopic examination showed macular degeneration and papillary atrophy. At the age of 9, myoclonic jerks were observed; subsequently, generalized seizures together with failing vision, mental deterioration, and visual and auditory hallucinations appeared. Brain MRI showed severe cortical and subcortical atrophy. A skin biopsy detected the presence of 'finger-print' inclusions in the cytoplasm of smooth muscle fibers. Late infantile NCL (Jansky-Bielschowsky disease) was diagnosed. FDG/PET revealed a severe reduction of metabolism in all the cortical and subcortical structures. A regional analysis of the distribution of the tracer revealed marked bilateral hypometabolism, particularly in calcarine, lateral, occipital, and temporal cortices and in the thalamus.