That's equal to 6.8 per cent of internet-based commerce.
Forrester's newest study concludes that m-commerce is set for a massive boom, up from €1.7 billion last year.
The forecast is based on surveys of 14,000 consumers in France, Germany, Italy, the Netherlands, Spain, Sweden, and the UK.
It reckons easy to merchandise categories such as books, DVDs, music, and ticketing, which lend themselves to mobile-specific features such as immediacy and location, will grow most rapidly.
Key findings include:
* The UK will be the most active market, with sales of €6.1 billion by 2017 – compared to €4.1 billion in Germany, and €3.1 billion in France.
* The number of active mobile shoppers will rise from 7.6 million in 2011 to more than 79 million in 2017.
In his blog on the subject, Forrester analyst Martin Gill reflected that the pressure is on retailers to respond to the changing habits of consumers by improving their mobile strategies.
He said: "Retailer enablement of mobile experiences lags a little in many European countries right now, particularly in southern Europe.
"It’s time that eBusiness executives stopped talking about mobile as something to do in the future and started enabling great, multi-touchpoint shopping experiences with mobile at the heart.
"Be under no illusions – mobile is here in Europe, and while shoppers aren’t going to ditch their laptops overnight, mobile, and in particular the smartphone is an increasingly influential touchpoint in both on- and offline commerce."