There was a time when no tobacco company could be beaten in a liability case, but it's gotten almost impossible to claim, with a straight face, that smoking doesn't cause lung cancer, emphysema, and other diseases. Juries are starting to respond, so don't lose hope.
If you're diagnosed with lung cancer caused by smoking, be aware that there may be a statute of limitations on how long you have to file a lawsuit against a tobacco company. This may vary from one state to another, so don't hesitate to start looking for a lawyer to represent you.