Prevalence of PIMs and PPOs. Results The sample included 161 individuals, with a mean age of 84.7 years (SD = 6.35), 68.9 % being female. A total of 807 PIMs and 90 PPOs were identified through the application of the three set of criteria. The prevalence of PIMs using the most recent version of the Beers criteria was 85.1 and 42.1 % for independent and dependent of diagnosis, respectively. The Portuguese adaptation of this same tool indicated a lower prevalence of PIMs, 60.3 and 16.7 %, respectively. The prevalence of PIMs using the STOPP criteria was 75.4 %, whilst the prevalence of PPOs, using START, was 42.9 %. There were significant differences in the mean number of PIMs detected depending on the tool used. (p < 0.001). Conclusions The application of the studied criteria in an elderly sample enabled the identification of a notable amount of PIMs and PPOs, indicating there is room for improving the quality of care. The variation in prevalence indicates careful choice of the tool is a prerequisite for engaging in medication review. Using START/STOPP criteria enabled a more holistic approach to the quality of prescribing in the elderly, highlighting low levels of cardiovascular risk prevention and abuse of psychotropic drugs, aside with system failures largely preventable by electronic prescribing and alert generation.