Dementia is a known predictor of mortality, but little is known about disease duration. We therefore aimed to investigate the impact of dementia on survival by estimating years lived with the disease, in total and in different severity stages, and by comparing dementia to other major chronic disorders such as cancer and cardiovascular disease (CVD). During a 7.4-year follow-up of the Kungsholmen project, 371 incident dementia cases of the 1,307 dementia-free persons, aged 75+ at baseline, were clinically diagnosed (DSM-III-R criteria). Diagnoses of cancer and CVD were obtained from the national Stockholm Inpatient Registry System, active since 1969. Disease duration, hazard ratio (HR), and potential years of life lost (PYLL) were derived from Kaplan–Meier survival estimation, the Cox model, and standard life-table analysis, respectively. Dementia was a significant predictor of mortality (HR=1.7; 95% CI: 1.47–1.92) after adjustment for several covariates including comorbidity, accounting for 16% of all deaths. The mean (±SD) survival time after dementia diagnosis was 4.1 (±2.6) years, and more than 2 years were spent in moderate (14-month) and severe (12-month) stages. Women with dementia lived longer than men, as they survived longer in the severe stage (2.1 vs. 0.5 years among 75–84-year-old women compared to coetaneous men). The PYLL were 3.4 for dementia, 3.6 for CVD, and 4.4 for cancer. We found a similar impact of dementia and CVD on survival, but following diagnosis, persons with dementia, and especially women, spent half of their remaining lives in the severe disabling stages of the disease.