Cognitive, haemodynamic and EEG lateral asymmetries have been quantified in 20 patients with Primary Degenerative Dementia (PDD) and in 20 age-matched normal volunteers. Normalized asymmetry scores were calculated from the data obtained with a test battery, with SPECT and with quantitative EEG. Significant correlations were found between cognitive, haemodynamic and EEG scores in patients but not in controls. The functional asymmetries correlated to the Mini Mental State (MMS) score, the lowest MMS values being observed in patients with right hemisphere predominant impairment. Besides, in these patients, a significant correlation was observed between age at onset and MMS score so that, in this subgroup only, the earlier the onset the more severe the disease. Finally, the prevalence of pronounced functional asymmetry seemed to be higher in our male patients. Our study shows that lateral asymmetries are frequent in patients with PDD and that preferential lateralization of the abnormalities should be given further attention, especially with regards to age, sex and overall severity.