Aims: Frail elderly patients who have multiple illnesses do not fare well in modern health care systems, mainly due to a lack of care planning and flawed communication between health professionals in different care organisations. This is especially noticeable when patients are discharged from hospital. The aim of this study was to explore health care professionals’ experience of obstacles and opportunities for collaboration. Methods: Health professionals were invited to participate in three focus groups, each consisting of a hospital physician, a primary care physician, a hospital nurse, a primary care nurse, a municipal home care nurse or an assistant officer, a physical or occupational therapist and a patient or a family member representative. These individual people were then asked to discuss the obstacles and opportunities for communication between themselves and with the patients and their relatives when presented with the case report of a fictitious patient. Content analysis was used to identify categories. Results: Several obstacles were identified for effective communication and care planning: insufficient communication with patients and relatives; delayed collaboration between care-givers; the lack of an adequate responsible person for care planning; and resources not being distributed according to the actual needs of patients. The absence of an overarching responsibility for the patient, beyond organisational borders, was a recurring theme. These obstacles could also be seen as opportunities. Conclusions: Obstacles for collaboration were found on three levels: societal, organisational and individual. As health care professionals are well aware of the problems and also see solutions, management for health care should support employees’ own initiatives for changes that are of benefit in the care of frail elderly patients with multiple illnesses.