Aims and objectives: To establish a screening instrument for identifying older hospitalised patients at risk for functional decline by comparing the predictive values of three screening instruments: identification of seniors at risk, care complexity prediction instrument and hospital admission risk profile. Background: After being hospitalised, 30-60% of older patients experience a decline in functioning, resulting in a decreased quality of life and autonomy. Design: A prospective cohort study. Methods: Included were patients, aged 65 years and older, acutely admitted to a general internal ward of a university teaching hospital. Within 48 hours after hospital admission, baseline data were completed--demographic, cognitive, social and pre-admission functional status and the screening instruments. Three months after discharge, functional status was measured by telephone interview. The Katz index was used to measure functional status (six activities). Functional decline was defined as a decline of at least one point on the Katz index at three months after discharge compared to pre-admission state. Results: Included were 177 patients; mean age was 77.6 years and 51.7 % were male. Functional decline was found in 27.8% of all patients. Sensitivity, specificity and area under receiver operating curve for identification of seniors at risk (ISAR) were 93, 39% and 0.67, respectively. The corresponding results for the care complexity prediction instrument (COMPRI) were 70, 62% and 0.69 and for the hospital admission risk profile (HARP) 21, 89% and 0.56. Conclusion: The discriminative values of both identification of seniors at risk and care complexity prediction instrument are fair. Hospital admission risk profile shows the poorest results. Identification of seniors at risk shows the best ability to predict those patients at risk for functional decline and seems to be the easiest instrument in clinical practice. Relevance to clinical practice: Identifying patients at risk for functional decline is a first step in prevention, followed by geriatric assessment and targeted interventions. Studying the validity of existing instruments is necessary before implementation in clinical practice. (aut. ref.