Abstract Background With the improvement of life expectancy, the world faces increasing demands for care of older persons. In this manuscript, we define the characteristics of primary informal caregivers (PIC) of patients aged 75 years and older admitted to geriatric day hospitals (GDH) in Belgium. A PIC is defined as the person who most often provides care and assistance to persons who need to be cared for. We describe PIC socio-demographic characteristics, satisfaction, burden and wishes about caring; the type of assistance provided and received, their self-rated health, socio-demographic and medical characteristics of proxies, in particular the presence of behavioural disorders. Methods We conducted a cross-sectional study in 25 GDH. Participants Four hundred seventy-five PIC of patients ≥75 years and their proxies. PIC completed a questionnaire at the GDH assessing burden by Zarit Burden Index-12 (ZBI-12), self-rated health, social restriction due to caregiving and financial participation. We compared ...