dear user, i understand your concern and appreciate your thoughts of qutiing smoking . you enquired about lung cancer and smoking - so yes smoking is the most major risk factor for lung cancer , and the risk is about 25 times more than non smokers. however no one can definitely tell from the symptoms that you have reported - tiredness,diziness that you have lung cancer or not as they may be the features ( not must) associated with lung malignancy along with cough,blood in sputum,hoarseness of voice, weight loss etc . not every smoker contracts lung cancer , and worrying is not going to help you in this regard -instead you have to act go visit a physician and gets yourself evaluated with physical examination and investigations- the tiredness and dizziness can be due to some other cause as well - quit smoking !! i know its difficult but not impossible - you can take help of a psychiatrist/addiction speciialist for that - drink a lot of water , do some deep breathing exercises , discuss the issues with family and friends and hopefully you will be able to quit smoking. any followup queries are welcome - if satisfied please rate the answer