This project explores the effects of specialized computer-based cognitive rehabilitation (CBCR) targeting executive functions in three groups of patients: Stroke, Cardiac Arrest and Parkinson's Disease. The effect of specialized CBCR is compared to completing generally cognitively stimulating activities on a computer. A total of 600 patients (400 with stroke, 100 after heart attack and 100 with Parkinson's disease) is expected to be enrolled. All patients will complete a neuropsychological test battery assessing executive functions at inclusion, directly after the eight-week training period and at follow-up three months after the end of the intervention period. Furthermore, all patients will answer questionnaires concerning quality of life and ADL-measures at baseline, after the intervention and at follow-up. All patients will train for a period of 8 weeks, 5 times a week for 60 minutes regardless of their group allocation.