Abstract Oxidative stress is associated with Alzheimer's (DAT) and vascular (VD) dementias, as well as Type II diabetes mellitus (DIAB) and affected by hypoglycemic therapy. The population ( n=122; males=60; mean age=72.57±7.06) consisted of controls (CTR), DAT and VD patients, with (DAT+DIAB, VD+DIAB) and without concomitant DIAB, resulting in six groups where the antioxidant profile was determined: copper–zinc superoxide dismutase (SOD), thiobarbituric acid reactive substances (TBARS), and total antioxidant capacity (TRAP). The results were analyzed using a two-way ANOVA design and Bonferroni statistic. The ANOVAs yielded significant differences between groups for all components of the profile: SOD, p=0.00000006; TBARS, p=0.0000012; TRAP, p=0.0000003. The significance level for comparisons between groups was set at α=0.05. The comparisons DIAB vs. CTR, DAT+DIAB vs. DAT, and DIAB demented vs. DIAB non-demented resulted significant for all variables. VD+DIAB vs. VD resulted significant for all variables except TRAP. The antioxidant profiles of DIAB and CTR are different. The differences cannot be directly related with what is observed in dementias. The differences in profiles of demented and non-demented are somewhat hidden when demented patients are affected by a concomitant DIAB condition and/or hypoglycemic treatment, thus conditioning the diagnostic value for dementias of the profiles.