Though language problems and tax issues deter many from experimenting with cross-border shopping, other consumers worry about when or whether the products will be delivered - and how to seek redress if purchases fail to arrive intact.
At present, four separate EU directives cover consumer rights, some dating from two decades ago and therefore predating the era of Internet shopping.
Although minimum standards apply across the EU, many countries apply stricter rules, thereby creating a patchwork of different guarantees, complicating the European single market. For example, the current cooling-off periods vary from 7 to 14 days, the European Commission says.
The proposals, to be put forward Wednesday by the European consumer affairs commissioner, Meglena Kuneva, will try to rationalize the legal framework to offer more reassurance to online customers.
Cécile Grégoire, senior adviser for payment systems at Eurocommerce, a trade association for retail, wholesale and international trade interests in Europe, said she welcomed the move in principle.
"Anything that would enhance the possibility for e-commerce across borders is important," she said. "It is important for large firms, and even more for small firms, to be able to open new markets and some type of harmonization is generally needed."
The commission noted the widely varying prices for merchandise across the European Union. For example, in March a Panasonic Lumix DMC-FZ8 digital camera was offered for sale in Britain for the equivalent of €198, while in Ireland it was €254, in Belgium it was €276 and in Finland it was €306.
With increased competition among Internet retailers, the expectation is that prices would decline overall.
Under the commission proposal, which needs the approval of national governments and the European Parliament, a common cooling-off period of 14 days would be established.
In addition, prices and terms and conditions of sale would have to be explained on the sellers' Web sites, and retailers would be prohibited from including on sites preselected boxes for added-cost options. Consumers would have the right to be reimbursed for money paid for preselected options.
Merchandise would have to be delivered within 30 days and the sellers would be responsible for the cost of any damage to the product in transit.
The legislation would also require a list of prohibited contractual terms - including terms that allow businesses to substitute one product for another without specifying a reason.