PayPal is the most popular method of online transactions throughout the world. It provides security and quicker transactions at the time of need.
If you are living outside the United States, you can make transactions using the PayPal at European sites, but in case of US poker players, you will experience a hard time in getting deposits using PayPal.
Paypal is considering to enter US Poker Gambling industry, particularly in New Jersey with full implementation in 2015. Paypal is in talks with NJ Division of Gaming Enforcement (DGE) to accept online poker payments in any US jurisdiction.
However, there are some websites such as BetOnline Poker, Sportsbook Poker, Lock Poker, and Carbon Poker that accept PayPal as a payment method from US.