BackgroundAdvance care planning (ACP) allows the definition of goals and preferences for future health care, improving communication between patients and caregivers. Portuguese Advance Directives (PAD) ensure a living will and/or the assignment of a health care proxy (HCP). Knowledge on PAD and HCP is low, and the influence of demographic factors is still not clear. We intend to identify sociodemographic features associated with knowledge on PAD and HCP, and the registration of PAD.MethodsPatients in palliative care and their caregivers were included, and sociodemographic data was acquired. Participants were asked about their previous knowledge of PAD, the role of an HCP, and about previously writing a PAD.ResultsA total of 60 patients and their caregivers were included, with differences regarding age (p < .001), gender (p = .003), education (p < .001), job (p < .001), marital status (p = .043), and access to the internet (p = .003), but not regarding religion (p = .21). 13.3% were aware of PAD, 15.0% were aware of HCP, and 5.0% previously filled a PAD. Non-Catholic participants were significantly more aware of these three topics.ConclusionsOur results are partially different from other Portuguese reports, probably due to differences in the populations, but consistent with results from other countries. Reports on the influence of religion in ACP are conflicting, with similarities in religious values between patients and HCP influencing end-of-life decisions. Improving education is necessary, namely in palliative care. There is low awareness of PAD and HCP in palliative care, and there is higher knowledge on these topics among non-Catholic individuals.Trial registration: ClinicalTrials.gov ID NCT05090072. Retrospectively registered on 22/10/2021.https://clinicaltrials.gov/ct2/show/NCT05090072?term=NCT05090072&cond=Advance+Directives&draw=2&rank=1