Free attractions welcomed double the number of visitors in 2015 than those which charge for entry.
Research by Glasgow Caledonian University found that more than half of Scotland’s castles, monuments and museums have an entry fee.
More than 41 million people flocked to free attractions last year, with numbers up by 1.6 per cent on 2014.
Free Edinburgh attractions such as the National Museum of Scotland and Scottish National Gallery continue to draw huge numbers of visitors, whilst 67 per cent of all Greater Glasgow attractions are free admission, amassing more than 17 million visits.
The detailed data - which covers 720 Scottish attractions - showed a 2.2 per cent overall increase across the country, with attractions in the Kingdom of Fife boasting the greatest increase in visitors and the greatest spend per visit.
It also found transport-themed attractions like the Falkirk Wheel, Edinburgh Bus Tours and the Strathspey Steam Railway were particularly popular in 2015, recording a collective 10 per cent increase.
Professor John Lennon, Director of the Moffat Centre for Travel and Tourism Business Development at GCU, said: “It may come as no surprise that tourists love free attractions, but paid attractions can take solace that overall visit numbers have also increased.
“Scotland boasts a fantastic breadth of options for tourists and the Visitor Attraction Monitor provides Scottish attractions with detailed, consistent and reliable data to shape their future planning.”
The findings follow the results of the top ten tourist attractions revealed in February, which showed seven Scottish attractions achieved more than one million visitors each.
Edinburgh Castle remained Scotland’s most popular attraction overall, with over 1,568,500 visitors.