Polls opened at 7am in what is the second referendum for Scots in as many years.
In 2014 voters north of the border opted by 55 per cent to 45 per cent to remain part of the UK after a referendum on independence.
But First Minister Nicola Sturgeon has repeatedly warned that result could be revisited if Scotland is “dragged” out of Europe against its wishes, if the UK as a whole opts for Brexit.
While voters north of the border are expected to back remaining part of the European Union, the picture across the UK is less clear.
Ms Sturgeon said yesterday that “Scotland can have a big impact on the final vote”, with voters north of the border potentially keeping the UK in the European Union.
She has however already revealed Scottish Government officials have been working on contingency plans for what could happen if the overall result is to leave the EU.
Ms Sturgeon and the leaders of the four other parties at Holyrood - Ruth Davidson of the Conservatives, Labour’s Kezia Dugdale, Liberal Democrat Willie Rennie and Patrick Harvie from the Scottish Greens - have all been campaigning for a Remain victory.
But Ukip’s Scottish leader David Coburn MEP said he believed a majority of Scots could vote to quit the EU.
“Everyone is saying they are voting to Leave, and I find very few people who say they are voting Remain,” he said while campaigning in Edinburgh on Wednesday.
“I think there is a majority for Leave in Scotland, or it is very close.”