It's still tough to get mobile users to pay for games. Nearly three-quarters of the 98.4 million mobile users in France, Germany, Italy, Spain, the United Kingdom and the United States who played a mobile game in December played a game that came already installed on the handset, according to M:Metrics.

The market research company said that 38.5 million (8.8%) of mobile subscribers played a game they had downloaded and stored on their phones, compared with 35.3 million (8.7%) who had done so in December 2006.

Only 14.4 million, or 3.3%, of mobile subscribers in the United States and Western Europe downloaded a game in the month, compared with 14.6 million (3.6%) in December 2006.

The preference for free mobile games goes beyond merely not wanting to pay for new games, according to Seamus McAteer, chief product architect and senior analyst at M:Metrics.

"One of the greatest challenges facing publishers by the growing adoption of smartphones is the wide availability of free or pirated content for these devices," Mr. McAteer said.