Aim: The aim of our study is to investigate the frequency, type and risk factors for delirium in the acute stage of stroke and after surgical intervention, using a specific diagnostic tool designed for the serial delirium assessment in the ICU setting: the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU). Methods: A cohort prospective observational study was performed in stroke patients admitted to the University Hospital within 24 hours after the stroke onset and in a group of patients who underwent planned surgery for spondylosis or pulmonary lesions. The data from the first 65 consecutive acute stroke patients (aged 72.1 + 11.1 years; 33 women and 32 men) and from 14 surgical patients (aged 62.5 + 10.7 years; 4 women and 10 men) were preliminary analysed in this pilot study. Results: An episode of delirium was observed in 31 acute stroke patients (48 %). The CAM-ICU showed a sensitivity of 98.9%. The mean duration of the delirious episode was 6.4 + 5.6, range 2-19 days, with the beginning 1-5 days after the onset of stroke. Delirium was significantly associated with pre-stroke dementia, age > 75 years, right hemisphere stroke, intracerebral haemorrhage and male gender. There was no episode of delirium observed in the surgical control group. Conclusion: Delirium is a frequent condition in acute stroke patients, if serially assessed on a daily basis with a validated diagnostic instrument. Beside various risk factors, stroke itself serve as an important risk factor for delirium compared to great surgery.