Yep, Orangeman's right. Even though the THC and other cannabinoids in weed seem to be responsible for lowering the risk of lung cancer in those who smoke it, weed still contains far more carcinogens and irritants than cigarette smoke (or no smoke). It is associated with a higher risk of pulmonary infections and inflammation and increased risk of bronchitis and pneumonia. THC itself is a beneficial expectorant and broncho-dilator, but THC isn't all you're getting when you smoke weed. Your lungs are getting all the crappy stuff, too, when you inhale smoke. If you're having chest pains and coughing, it may be time to try vaporizing or eating your cannabis instead of smoking it.