We describe a patient in whom motor neuron disease and frontal dementia showed concomitant development. This patient underwent a detailed and sequential neurolinguistic assessment, which indicated an alteration in language planning, language comprehension, and morphosyntactic operations. He showed also attention deficit, abstract reasoning disturbances, and prosopoagnosia which became worse during the year follow-up. We suggest that a more specific and sensitive neurolinguistic and neuropsychological test battery must be used to detect and study the entire disruption of cognitive processes in frontal dementia related to motor neuron disease.