I guarantee you that you will not like what these say if you are a die hard smoker, but there are some very interesting facets to these studies.

Effects of cannabis on pulmonary structure, function and symptoms -- Aldington et al. 62 (12): 1058 -- Thorax
Compared to smoking cigarettes.

Caution on this one, federally sponsored, but sounds like a legit study
Respiratory symptoms and lung function in habitual... [Am Rev Respir Dis. 1987] - PubMed result
Compares to non smokers, cig smokers and mj smokers.

Arch Intern Med -- Effects of Marijuana Smoking on Pulmonary Function and Respiratory Complications: A Systematic Review, February 12, 2007, Tetrault et al. 167 (3): 221
a different opinion for sure

Effects of cannabis on lung function: a population... [Eur Respir J. 2010] - PubMed result


[Pneumotorax and cannabis] [Minerva Chir. 2009] - PubMed result
I wish to comment that as a former paramedic, I have treated patients who acquired a spontaneous pnuemothorax from holding the smoke during a cough fit. This can expand what are called 'blebs' and cause a pneumothorax.

The studies vary greatly and have similar findings also. Face it smoking is bad no matter what you smoke. Makes me want to refine my concentrate making.
WashougalWonder Reviewed by WashougalWonder on . Medical Journal References Being unable to find references that I did not feel were biased in any regard as related to cannabinoids being good, bad, or indifferent to the human body. No rats, mice, dog, or monkey studies...no jest as there is valid documentation that shows cannabanoids effect humans differently. Other requirements are that the author(s) are medical (MD) doctors or carry a doctorate in human medical pharmacology. We are talking journals such as the American Heart Association, or New England Journal Rating: 5