Argyll & Bute Council and Highland Council have researched the issue - dubbed 'supersparsity' - for the Convention of Scottish Local Authorities, as part of its work to persuade the Scottish Executive to increase resources for local government. They define supersparsity as the number of people living more than 25 miles from settlements of at least 7,000 residents.
In Argyll & Bute, this affects 18,000 people, some 20% of its population. In Highland 54,000 people, some 26% of the population, live in such remote areas.
Argyll & Bute leader Allan Macaskill (Ind) said: 'The report demonstrates quite clearly that it costs the council an additional£2.6m to provide education, and an additional£200,000 to provide some planning and social work services to remote and rural areas.'
Highland Council convener Alison Magee (Ind) said: 'The extremes that exist in Highland cannot be addressed fully using conventional methods.'