yes weed does give you lung cancer although it isnt nearly as bad as ciggaretts,ciggarett resin(for lack of a better word) cakes to your lung much worse than marijuana resin and isnt as easy to get rid of.cigs also have polonium-210 and many many other suspected carcenogens that are catalyst for cancer.so yes if you smoke cigs you have a much higher chance to develop cancer than smokeing weed alone.but smokeing anything is bad for you and could possably give you cancer wether it be tabbaco,marijuana,duct tape or your bed sheets rolled into a huge joint(hey if i ever have enough weed for that....)it will be bad for you and may give you cancer