The Lebanese pound is the national currency. However it is very easy to exchange US dollars, which are considered to be the country’s second currency. So if you have dollars, you don’t need to exchange them for Lebanese pounds. In most places, you can pay with dollars.
For the past 15 years or so, there has been a fixed exchange rate between US dollars and Lebanese pounds: US$1 = LBP 1,500.
For other currencies, the exchange rate will depend on their rates against the US dollar. By way of example, €1 was worth approximately LBP 1,900 as at November 2014.