Sorry guys, couldn't help posting a thing or two. There is no need for bank account to OPEN a paypal account. But you NEED TO HAVE A BANK ACCOUNT IN THE COUNTRIES as in the list provided by tudhikhel bro to say withdraw or even deposit.
Once you register your bank account, they will send you some amount to open transaction with the bank and then only your paypal account can accept transactions else it is just an account which can do nothing.
Yes, that is the actual case.
I have two paypal accounts (in two different names, of course). One is attached to the bank and another is not. I pay my bills and receive payments in the one not attached to the bank.
If I receive more than I pay then I will send the extra amount to my other paypal account to transfer it to the bank.
The bad thing is that paypal charges FEES everytime I send money from this account to another account. (Transferring money from Paypal to Bank is usually free)
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For those living in Nepal. If you wan't to earn something from internet like ziddu (it is crap!), or online ads etc. You can receive payment in Paypal in your account. You can pay your hosting charges etc through paypal. You can do your business in paypal. Earn, spend virtual money.
But you won't be able to take the money from paypal and eat momo in Baneshowr

But, that is true until you meet people like me, who has paypal account linked to their bank account. You can ask such 'trustworthy' friend to withdraw your money for you.