t revealed plans to invest £2.5bn across the UK, including upgrading 34 exchange areas in Scotland.
The company said 277,000 homes and businesses would be covered.
The best of the new connections will allow internet download speeds of up to 300Mbps. The regulator Ofcom calculated this year that the average connection speed in the UK is 6.8Mbps.
The exchanges receiving the new investment include parts of Aberdeen, Dundee, Edinburgh and Glasgow, as well as a number of smaller towns.
BT Scotland Director Brendan Dick said: "It marks a major investment in infrastructure, which will give the country a tremendous boost.
"Next-generation broadband is essential for our nation's economic growth, so it's brilliant to be ending 2011 on such a high note."
BT said the number of homes and businesses able to access the superfast network will reach 685,000.
The investment has been welcomed by the Scottish government.
Infrastructure and Capital Investment Secretary Alex Neil said: "We have set out our ambition for all of Scotland to have access to next-generation broadband by 2020, with significant progress to be made by 2015.
"It is an important part of the Scottish government's economic strategy."
Source: BBC Tech News