Introduction: According to previous estimates, 40% of dementia cases globally may be attributed to 12 potentially modifiable risk factors. Methods: We calculated national population attributable fractions (PAFs) for each risk factor and modeled the effects of proportional reductions in risk factor prevalence on dementia prevalence by calculating potential impact fractions (PIFs) for each factor. Results: The overall adjusted PAF for all risk factors was 35.2%. Physical inactivity, hearing loss, hypertension, and obesity accounted for 64% of the total prevention potential. The overall adjusted PIF was 4.1% at 10% risk factor prevalence reduction and 8.1% at 20% risk factor reduction. Discussion: Estimates of the potential for the prevention of dementia should be based on country-specific data on risk factor prevalence, as estimates based on global risk factor prevalence have limited relevance from a national perspective. Physical inactivity, hearing loss, hypertension, and obesity could be primary targets for prevention of dementia in Denmark. Highlights: Overall adjusted PAF for potentially modifiable dementia risk factors was 35%. Physical inactivity, hearing loss, hypertension, and obesity had the largest prevention potential. Estimates of prevention potential should be based on national risk factor prevalence.