There are no specific licensing hours in Warsaw, and should you want to, you can sit in one of the flashy bars in the old town from dusk until dawn soaking up the local booze (around 50p per bottle of beer) and listening to the DJ, before getting breakfast and going back to your hotel.
Most of the newer bars are very tourist friendly, and have entertainment on offer.
Ground Zero is the most popular club in the city, and on the weekend, it is filled to capacity with revellers dancing to music played by big name DJs from all over Europe.
If you fancy a gamble in Warsaw, then you can visit one of the main casinos such as the Orbis, although you should be aware that a passport and smart dress are required.