Yes, many of the popular poker sites such as Party Poker, Pokerstars, Pacific Poker, and Ultimate Bet have a number of poker celebrities or poker professionals that play there. Some professional poker players that play online are Phil Helmuth Jr, Phil Ivey, Annie Duke, Kathy Leibert, Howard Lederer, Gus Hansen and Daniel Negraneau to name a few. So yes, it’s quite common for professionals to play poker online.