Visitors to the Outer Hebrides, Shetland and Orkney were questioned for a study on tourism to the islands in 2012/13.
The survey found that more than 425,000 people visited the islands that year, with their scenery, landscapes, archaeology and history proving the main draws for tourists.
Around three quarters of visitors said they would be likely to return for a holiday in the next five years, and around 80% of visitors said they were "very satisfied" with their trip.
The islands visitor survey survey was carried out by Scotinform and Reference Economics, in partnership with the areas' local authorities, Highlands and Islands Enterprise and tourism body VisitScotland.
Mike Cantlay, chairman of VisitScotland, said the islands are "incredible places to visit".
He said: "Tourism is a key economic driver for many of Scotland's islands as the islands visitor survey has clearly demonstrated.
"It is great to see that visitor numbers are rising, particularly given the challenging economic climate and that tourism continues to prove it's a resilient and sustainable industry."
The survey, conducted between October 2012 and September 2013, asked almost 4,000 people a range of questions as they left Orkney, Shetland and the Outer Hebrides, including the reason for their visit, where they stayed and what they visited during their trip.
It found that over that period, Shetland welcomed 64,655 visitors with a total spend of £16 million. Orkney attracted 142,816 visitors, who spent more than £31 million in the local economy. The Outer Hebrides was visited by 218,196 people, who spent more than £53 million over the 12-month period.
Tourism Minister Fergus Ewing said: "The fantastic results from the islands visitor survey are a credit to the people working in the hotels and tourism sector on our islands, who give our guests a warm welcome and enjoyable holiday.
"With beautiful scenery, rich history and diverse culture, it's no surprise that Scotland's islands are attracting more visitors and encouraging them to spend more and stay longer.
"In this Year of Homecoming as we prepare to host both the Commonwealth Games and the Ryder Cup, I am confident that 2014 will be a remarkable year for tourism."