The continuous increase in elderly and oldest-old population, and subsequent rise in prevalence of chronic neurological diseases like Alzheimer's disease (AD) and Parkinson's disease (PD), are a major challenge for healthcare systems. These two conditions are the most prevalent neurodegenerative diseases in older persons and physicians should engage treatment for these patients. In this field, Randomized Clinical Trials (RCTs) specifically focused on elderly populations are still lacking. The aim of this study was to identify RCTs conducted among AD and PD and to examine the difference between mean age of enrollment and incidence of these two neurodegenerative diseases. We found that the scenario is different between PD and AD. In particular, the enrollment for PD trials seems to include younger persons than AD, although the incidence of both diseases is similar and highest after 80 years old. The consequence of these results could influence conclusive guidelines of treatment in older parkinsonian patients.