Graphic showing the brain of an elderly man affected by Alzheimer's
A charity has called on the Scottish government to invest £15m each year for the next five years to help people with dementia.
Alzheimer Scotland said the number of people diagnosed with the condition in Scotland could increase by almost 60,000 within a generation.
This would put increased pressure on dementia services, the charity warned.
The government said dementia was a "national priority". It will publish a new dementia strategy in the spring.
Alzheimer Scotland said £15m a year would help local authorities and NHS boards fund early intervention to help delay the onset of dementia, which can have a "significant impact" in the social and economic cost.
Chief executive Henry Simmons said: "There is no greater public health issue than dementia.
"An increase in numbers from nearly 70,000 today to around 127,000 within a generation leaves us with no option but to prepare, plan and provide for increasing need and demand.
"We can meet these needs - but we must act decisively and we must act now."
He argued that current dementia services were not cost-effective as they often intervene too late, when the person involved has already reached "crisis stage".
The charity also called for the UK and Scottish governments to increase funding for research into dementia.
Studies suggest that if the symptoms of dementia can be delayed by five years, health and social care budgets would be halved, the organisation said.
A spokesman for the Scottish government said: "We have already taken decisive action to set a national target on early diagnosis, are investing in support immediately after diagnosis and have issued specialist guidance on dementia patients to A&Es and acute hospitals.
"As Scots are living longer, the number of people affected by dementia is likely to increase by around three quarters over the next two decades.
"That's why planning for the future is vital and we expect to publish our new dementia strategy in the spring."