<b><i>Background/Aims: </i></b>This study was designed to develop a practical risk score for predicting 5-year survival after the diagnosis of dementia. <b><i>Methods:</i></b> Using the Paquid Study (prospective, population-based, long-term cohort study), we created a prognosis score with incident cases of dementia and validated it in another prospective, population-based, long-term cohort study, the Three City Study. -<b><i>Results: </i></b>Among the 3,777 subjects enrolled in the Paquid Study, 454 incident cases of dementia were included in this study. After a 5-year follow-up period, 319 (70.3%) were deceased. The score was constructed from three independent prognostic variables (gender, age at diagnosis and number of ADL restricted). The discriminant ability of the score was good with a <i>c</i> index of 0.754. Sensitivity was 64.7% and specificity 76.3%. In the validation cohort, the discriminant ability of the prognostic score with <i>c</i> statistics was 0.700. Sensitivity was 26.3% and specificity 95.4%. <b><i>Conclusions:</i></b> The prognostic factors selected in the predictive model are easily assessable, so this simple score could provide helpful information for the management of dementia, particularly to identify patients with duration of the disease greater than 5 years.