There are as many mobile handsets on a Japanese commuter train as on the commuter trains of any other rich economy. Yet in Japan, the telephones are curiously silent. Instead of speaking into sleek silver gadgets, users are busy sending e-mails or downloading pictures of their favourite pop stars.

Japan's growing band of e-mail junkies has driven the phenomenal success of NTT DoCoMo's i-mode, the mobile phone service which offers continuous internet access. According to DoCoMo, the largest mobile phone operator in Japan, by April, its mobile internet service boasted 22m subscribers - almost one in six Japanese.

European operators look on with envy - and desperation. Europe's wireless application protocol (Wap) internet phones have failed to make an impact. Meanwhile, operators have spent billions acquiring third generation (3G) mobile licences to support even more advanced services. The more European telecom shares are hit by scepticism about Wap and worries about the debt taken on to pay for new investment, the more European operators turn to Japan for inspiration and hope.

Hence the importance of understanding the reasons for i-mode's success - and the worrying possibility that western excitement about wireless internet services may be based on several i-mode myths.

To begin with, in the west there is a widespread misperception that the wireless internet is all about technology. One view is that once i-mode-style packet switching replaces the circuit switching of traditional telephony, the demand for wireless internet services should take off. With packet switching, the telephone can be continuously connected to various websites. It also lowers the cost of sending data.

I-mode does have technical advantages. For one thing it uses a variant of HTML, the standard script of the internet, unlike Wap which runs on a completely different language. In addition, packet switching saves users the hassle of calling up a website every time they need to interact with one.

But packet switching is not everything. J-Phone, a smaller competitor to DoCoMo, has been able to amass 3m subscribers to its J-Sky internet service even though it uses circuit-switched technology.

Another common European view is that the faster access speeds of 3G networks will finally make possible the wireless internet revolution. But at 9.6 kilobits per second, i-mode's data transmission rate can hardly be described as fast. Moreover, to the extent that speed matters, the news from Japan about third-generation telephony is bad.

Japan will be the first to launch 3G, and DoCoMo has tested equipment provided by NEC in a full-scale trial in southern Japan. Recently, however, DoCoMo sent shivers through the industry when it revealed that only when used by a few users at a time does w-CDMA do everything its designers promise. The limits of available radio spectrum mean that the standard can't simultaneously provide the very high data speeds needed for video and sound transmission to large numbers of users over long periods.

In densely populated cities, it would be more practical to download short, 10- or 15-second clips of music and video. If customers like what they see, they can order a full-length recording of a pop song or sports event to enjoy at home downloaded over fixed telecommunications networks. That is one reason why DoCoMo was keen to tie up with America Online in developing services that combine the benefits of both fixed and mobile internet access.

Japanese operators are wary of technology for technology's sake. "Wap failed [in Europe] because operators concentrated too much on the technology rather than the content," says Keiichi Enoki, leader of the i-mode project team. "It is like worrying about the quality of television sets before you have any programmes."

By contrast, content has been central to DoCoMo's success. The secret lies, above all, in the variety of what is on offer. Amid the neon of Tokyo's Shibuya district, Japanese teenagers in knee-high boots dream of downloading the latest cute cartoon characters to decorate their screens. Besuited businessmen try their luck at a virtual fishing game, or check the latest scores of their favourite baseball team. "The package of content that we put together was the killer application that helped i-mode to take off," says Toshiharu Nishioka, manager of DoCoMo's gateway business department.

This points to yet another myth that has fed the frenzy of European operators: that by putting existing content, such as films and popular songs, on to mobile telephones, the mobile internet business will provide a quick and easy payback.

"In Europe there is an overly optimistic view that if they just take contents off the shelf it will offer them a huge business opportunity," says Kiyoyuki Tsujimura, DoCoMo's head of global business. Content will need to be tailored to the evolving needs of users and the limitations of what 3G can do.

Keiji Tachikawa, president of DoCoMo, notes that the winners in 3G will be the people "who are creative enough to find out what kind of content is most desirable in a mobile [phone] environment".

What is more, contrary to western expectations that services such as i-mode will work everywhere, this content is culturally specific.I-mode is, to some extent, rooted in the idiosyncracies of Japanese society.

As Jordan Roderick, chief executive officer of AT&T Wireless International, points out, in Japan the number of people owning personal computers is low compared to the US. In addition, US teenagers are far less mobile than Japan's youth.

The i-mode phenomenon has coincided with changing social behaviour, particularly among Japan's urban youth. "Young people have a very different attitude towards personal relationships," says Masahiro Yotsumoto, research director at the Dentsu Institute for Human Studies. "Instead of having one good friend, they prefer to have 200 mobile phone friends."

Sending short messages, such as saying good night to a friend, is one of the most popular uses of i-mode, Mr Nishioka points out.

The lack of real privacy in small Japanese houses has also helped to make mobile phones popular. "In Japan, especially for young people, their home is their cell phone," says John Barber, managing director of AOL Japan.

Even with i-mode's advantages, DoCoMo predicts that it may take four years to make a profit on 3G, and many more years to recover the cost of investing in 3G. Europeans may have to wait even longer.