The aim of this research was to study semantic abilities and their loss in mild cognitive impairment (MCI) and in dementia, while analyzing efficiency in the use of associative relations, within verbal and visuoperceptual modalities. Participants were split into 4 groups: 19 participants with amnestic MCI, 16 patients with mild Alzheimer disease (AD), 20 patients with moderate AD, and 20 healthy controls (HCs). All participants performed standardized neuropsychological tests and experimental (naming and semantic associations) tasks to evaluate verbal and visuoperceptual semantic abilities. We analyzed 4 associative relations (part/whole, function, superordinate, and contiguity) in both verbal and visuoperceptual code. Our results suggest a progressive impairment in semantic categorization knowledge, with worse performance in the AD groups relative to the MCI and HC groups. Our data show a different pattern in the 4 associative relations and the involvement of associative semantic relations already in the early stage of disease, as well as a different pattern of deterioration between verbal and visuoperceptual modalities. Our data indicate that the visuoperceptual semantic network appears to be less deteriorated than the verbal network in AD. The verbal semantic network may be more sensitive in detecting patients at an early stage of the disease.