Background: In order to address the challenges of an ageing population the Belgian government decided to allocate resources to the creation of geriatric day hospitals (GDHs). Although GDHs are meant to be a strategy to support general practitioners (GPs) caring for the frail elderly, few Belgian GPs seem to refer to a GDH. This study aims to explore the barriers and facilitating factors of GPs' referral to GDHs. Methods: A qualitative study using focus group discussions (FGDs) was conducted. Fifteen FGDs were organized in the different Belgian regions (Flanders, Wallonia, Brussels). Results: Contextual factors such as the unsatisfactory cooperation between hospital and GPs and organizational barriers such as the lack of communication on referral procedures between hospital and primary health care (PHC) were identified. Lack of basic knowledge about the concept or the local organization of GDH seemed to be a problem. Unclear task descriptions, responsibilities and activities of a GDH formed prominent points of discussion in all FGDs. Nevertheless a lot of possible advantages and disadvantages of GDHs for the patient and for the GP were mentioned. Conclusions: In the case of poor referral to GDHs, focusing on improving overall collaboration between primary and secondary health care is essential. This can be achieved by actively delivering adequate information, permanent communication and more involvement of PHC in the organization and functioning of GDHs. The absence of a transparent health care system with delineated role definitions, seems to hinder the integration of new initiatives like GDHs in the care process. Strategies to enhance referral to GDHs should use a comprehensive approach.