Statistics on PokerStars players is available on specialized resources that track the game history of all users of the largest poker room. In order to gain access to information on multi-table tournaments and SnG, you need to know your opponent's screen name.
Cash players’ statistics is only available on whotfru.info - this site provides its services for money. Cost of the services depends on the purchased package. You may also use the highstakesdb.com website, which tracks the game at the cash tables on the highest limits of PokerStars.
On the Internet, there are three most popular resources, where a user can find out his opponent’s statistics: number of played tournaments, average buy-in, profit per tournament, total income, etc. Here are the best sites where you may check PokerStars players' statistics by means of a screen name:
It’s also worth noting the playerscope.com website, which is gradually gaining more popularity among poker players.
You can familiarize with the poker room PokerStars in a detailed review from Cardmates.