The Consumers Association of Ireland is urging people to use only credit cards or Paypal when shopping for goods online.
The warning comes today, on "Cyber Monday" - the busiest online shopping day in the run up to Christmas.
55% of Irish people are expected to purchase gifts online this year with a total spend of €512 per person.
"Really of the utmost importance is that you be sure of the site you're on, that it has all the protections … that you would expect," said Dermot Jewell, CEO of the Consumers Association of Ireland.
"Where possible, always insist yourself, for protection, that you pay either through PayPal or using a credit card.
"We have a very positive legal structure here … that protects consumers when using a credit card."