Professional social network LinkedIn is getting serious about expanding outside the US to help grow its share of the social net market. In January, after months of speculation that the company was on the block, it finally admitted that yes, it had considered that option, but no, they had decided to press on themselves. At the same time, LinkedIn opened up a London office, hired former Alta Vista international GM Kevin Eyres as its continental MD., and is now concentrating on building its targeted advertising program as well as flogging its job recruitment product in Europe. IDG reports that in its European efforts LinkedIn is playing “catch up,” having only recently secured the linkedin.co.uk domain name after a domain dispute. It also only offers the site in English, limiting its European reach.

Currently, it has 20 million users worldwide, a fraction of MySpace with its 200 million users, and Facebook with some 70 million registered users. Five million of those users are in Europe and one million in the UK, its biggest user base outside the US. The company claims, however, that 1.3 million new visitors are joining a month. Of course, there’s also the argument that LinkedIn users are more valuable, as they are mostly working professionals, with an average age of 41, and an average income of £55,000 ($110,000). Hence, the company points out that their CPM rate is around £37.50 ($75) in the US, and £25 ($50) in the UK—which they claim is much higher than what MySpace can charge.

LinkedIn also has competition from Germany-based professional social net Xing, which reported it had 4.8 million users as of March. The site is available in 16 languages and has spent last year buying smaller social nets across Europe.

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