Objectives: Delirium is an acute onset syndrome of fluctuating course often observed in elderly patients post-operatively. Research has focused on aetiology and risk factors associated with delirium but tends to overlook cognitive deficits commonly observed in patients. The aim of the present study was to investigate memory and perception in patients with delirium and, furthermore, to compare and contrast the different cognitive functions affected in delirium with those affected in Alzheimer’s. Methods: Participants were screened for delirium before completing a short battery of cognitive tests. Participants: 52 participants over 65 years of age were recruited from orthopaedic trauma wards at the Edinburgh Royal Infirmary and the Memory Clinic at the Royal Victoria Hospital, Edinburgh. Each was placed into one of three groups; delirium (N = 19), Alzheimer’s dementia (N = 14), and no cognitive impairment (N = 19). Results: The control group performed significantly better on CERAD total recall and the CERAD percentage recall than the delirium and dementia groups. Additionally, the control group performed significantly better on the word list recognitions task than the dementia group. With regard to the perceptual tests it was found that the control group performed better than the delirium group, with the dementia group also performing significantly better than the delirium group in the incomplete letters task and the shape detection screening test. Conclusions: Patients with delirium do appear to suffer from visual perceptual deficits, but much more investigation is needed to establish whether these deficits underlie perceptual disturbances.