Semantic dementia (SD) is one of the main clinical forms of frontotemporal degeneration. The authors describe clinical and neuropsychological characteristics of two patients with SD with the atrophy of frontal regions of temporal lobes of the right and left hemispheres. The disturbance of the semantic structure of speech caused by the lesion of the left hemisphere and the prevalence of prosopagnosia and behavioral disturbances related to the atrophy of the right hemisphere have been identified.