A surge in complaints about products and services worth more than £133 million a year, many of which have been bought on the web, have been made to Citizens Advice Scotland.
However, many more complaints relate to payday loans and other financial products as well as housing, utility bills and travel.
Internet shopper Jackie Boyle was among 200,000 people who contacted the charity last year after spending £360 on furniture that she never received.
Ms Boyle, of Wishaw, North Lanarkshire, used her credit card to pay for two dining room chairs, which she was told would be delivered 16 weeks later.
The Spanish-based company had a glossy website and seemed trustworthy when she handed over the money. But the chairs never arrived.
She is now trying to get a refund from her credit card company after she failed to get her money back from the company.
"I'm hopeful I'll get my money back. I've since found out that the company I paid is the subject of thousands of complaints," said Ms Boyle.
"There are a huge number of people trying to get their money back from them and many have lost a lot more money than me."
"After what has happened, I would not advise anyone to buy anything from an online company unless you know them or have researched them and you know other people who have dealt with them successfully.
"I would never spend money again on a company that had a flash website but we didn't know anything about them."
She added: "I think a lot of these complaints do relate to people who have spent money online."
The scale of the rip-offs emerged as CAS takes up a beefed-up role from tomorrow representing people with complaints relating to the postal service as well as about water and energy bills.
It has already extended its remit to help people who have been affected by payday loans.
The charity is hosting a series of question-and-answer sessions this week on social networking site Twitter from 12.30pm to 1.30pm. Topics include debt, energy, post and cars.
Margaret Lynch, chief executive of CAS, said: "People in Scotland are paying too high a price for rip-offs and dodgy deals - in money, in time wasted and in worry and distress.
"Each year CAS's services help more than 200,000 people sort out consumer problems that are making their lives a misery - and we campaign to make sure they don't happen again."