AdMob this week released its May Mobile Metrics Report, which focused on Western Europe, and the results show mobile Internet usage is growing, particularly in Spain and Italy.

AdMob reports it has seen traffic double on average since it began tracking these markets in September 2007, with Spain showing the greatest percentage of growth on sites within the AdMob network and Ireland the least.

AdMob’s traffic grows with organic growth of sites in its network and with the addition of new sites, according to Jason Spero, vice president of marketing. Most of the European growth has been driven by organic growth of sites, he said, adding that the biggest drivers of Web usage are operator data pricing, network speeds, increased penetration of advanced devices and the viral spread of communities.

The report also noted that the iPhone is grabbing market share throughout Europe. It is now in the top 10 devices in France, Germany, the Netherlands and Spain, and it’s in the top 20 devices in every market where Apple has a formal operator distribution partnership.