Inflammation has been involved in the development of dementia in cerebrovascular diseases. To investigate the cellular activation of the peripheral immune system in patients with Alzheimer's disease (AD) and vascular dementia (VaD), we determined the presence of IL-18 and TGF-beta1 in the plasma by using ELISA. The levels of IL-18 and TGF-beta1 were significantly elevated in patients with AD and VaD compared to non-demented, age-matched subjects. We found an inverse correlation between the levels of IL-18 and TGF-beta1 in AD patients. In VaD patients, the correlation between IL-18 and TGF-beta1 reached a borderline positive value. Whereas, in the non-demented, age-matched subjects, a positive correlation between IL-18 and TGF-beta1 levels was observed. These findings indicate that IL-18 and TGF-beta1 elevation is associated with AD and VaD patients, confirming that the immune system might exert a remarkable role in the development and progression of neurodegenerative disorders. Moreover, as different modifications were detected in the patients affected by AD and VaD, we propose that IL-18 and TGF-beta1 plasma levels might represent possible differential biomarkers.