Drinks, perfume and designer goods can be more expensive in airport duty free shops than online, price comparisons show.
Shops in airport terminals trumpet the 'savings' available to those flying overseas, with shoppers often assuming the products will be cheaper.
But a look at a range of products on offer in the departure lounge stores shows many are available cheaper elsewhere.
Perfumes are among the products with the highest difference in price, with a number of brands cheaper online than at the airport.
A 100ml bottle of Burberry Touch for example is £24.75 at Fragrance Direct, half the £42.80 for which it is sold at airports by World Duty Free.
Meanwhile, a 90ml bottle of Versace Bright Crystal is £38.99 online as opposed to £54.85 in duty free stores.
Alcohol can also be cheaper in supermarkets. Tesco is currently charged £13 for a 1-litre bottle of Malibu, more than £3 less than it is at World Duty Free.
Fashion accessories are also less expensive online, with a pair of Bvlgari BV8144B sunglasses £207 in duty free, but £174 at sunglasshut.com.
Martin Lewis, from moneysavingexpert.com told MailOnline: 'Savvy shoppers know that duty free does not automatically mean everything is a bargain.'
Mr Lewis added: 'Duty free shops are the same as all shops, they have prices, it can be cheap for some things, it won't be cheap for other things.
'My advice is for people to get their phones out while they are in these shops and see if they can find things cheaper online.'
World Duty Free, which runs stores in airports around the UK, recently set up a pick-up service, meaning customers can order online before collecting their purchases ahead of their flight.
The company has said it offers 'year-round low prices' as opposed to the limit offers available in supermarkets and online.
A spokesman said: 'No retailer can ever promise that all its products will always be the cheapest in today's fast-moving retail world and we do not make this claim.
'The very small selection of offers identified does not undermine the World Duty Free proposition of offering consistent savings across a wide range of brands and products in our airport stores throughout the year.'
Duty Free products, those such as cigarettes and some spirits which are exempt of excise duty and taxes, are only available to customers travelling outside the EU.
However, a range of other items are sold in 'duty free' stores in airports available whether passengers are flying.