Just 61% of Scots have broadband, compared with 74% of people across the whole of the UK.
Broadband connection is particularly low in Greater Glasgow, where the figure is just 50%.
One reason why take-up is so low may be that a relatively high proportion of Scots never use the internet.
Ofcom's Scottish director Vicki Nash warned that with so many public services now available online, Scots were at risk of being left behind.
About 30% of adults in Scotland say they do not use the internet in any location, compared with 20% across the UK as a whole.
Just under two-thirds of Scots have a computer in their home but across the UK the figure is 77%.
Take-up of broadband was particularly low amongst those aged between 16 and 34, people aged 55 and people on a low income or lower down the social scale.
'No need'
Although there is some concern about the speed of broadband connections in some parts of the country, this is probably not the reason why such a high proportion of Scots have neither broadband nor a home computer.
Ofcom's research also found that the bulk of people who do not have the internet at home did not intend to get it within the next year.
Most of them said this was because they did not know how to use a computer, felt there was no need for broadband or even that they were too old to use the internet.
However, not all the findings were negative. People in Scotland aged between 35 and 54 were actually slightly more likely to have broadband at home than people across the UK.
The internet's increasing importance for both businesses and public services was also highlighted.
For instance, many councils are now placing public notices on a website and some observers believe fresh moves to try to remove the legal obligation to place them in the press are likely within the next few years.
Ms Nash said: "Despite increasingly sophisticated broadband packages available to more and more Scots, we are less likely than the rest of the UK to take up broadband.
"With an ever-increasing range of public services available online and the importance of the digital economy, there is a risk of Scotland being left behind."
Scots are still the least likely in the UK to have a broadband internet connection, according to a report from the communications regulator Ofcom.