Objectives : the study was designed to investigate the impairment of the ability to discriminate between nouns and verbs, resulting from the damage to the left-hemisphere, a condition which could lead to linguistic disorders proportionate to the depth and extent of the damage. Various experimental and clinical investigations have demonstrated that nouns and verbs may, independent of one another, become subject to dissociation as a consequence of various types of brain changes. Method: the subjects were 20 Persian speaking patients with aphasia (8 female and 12 males), aged 33-76, receiving treatment in speech therapy centers in Tehran. The data were collected through a Persian Aphasia Test. Findings: the descriptive and analytical research findings demonstrated a significant relationship between the ability to use nouns and the damage to the temporal lobe of the left hemisphere, near the angular gyrus and the corpus callosum. A similar relationship was found between the ability to use verbs and the damage in the frontal lobe of the left hemisphere. The important issue here is the difference in the location of damage to the areas of brain responsible for discriminating nouns and verbs, an issue that cannot be ignored.