Antineoplastic activity of cannabinoids
Antineoplastic activity of cannabinoids

Delta(9)-Tetrahydrocannabinol inhibits epithelial growth factor-induced lung cancer cell migration
Unbound MEDLINE | Delta(9)-Tetrahydrocannabinol inhibits epithelial growth factor-induced lung cancer cell migration in vitro as well as its growth and metastasis in vivo. Journal article

Smoking Cannabis Does Not Cause Cancer Of Lung or Upper Airways
CCRMG

No association between lung cancer and cannabis smoking in large study
IACM-Bulletin

Marijuana Smoking Found Non-Carcinogenic
Medical News: ATS: Marijuana Smoking Found Non-Carcinogenic - in Hematology/Oncology, Lung Cancer from MedPage Today

CLAIM #4: MARIJUANA CAUSES LUNG DISEASE
Erowid Cannabis Vault : Exposing Marijuana Myths

THC inhibits epithelial growth factor-induced lung cancer cell growth and metastasis in vivo.
http://marijuana.researchtoday.net/archive/4/7/1212.htm

Marijuana Ingredients Slow Invasion by Cervical and Lung Cancer Cells
Pot Slows Cancer in Test Tube

Marijuana May Fight Lung Tumors
Marijuana May Fight Lung Tumors

And there's more in the "Tobacco vs Cannabis" section in the link below. Apparently, although in some studies they have found that cannabis has more tars (but whose cannabis?, grown how? That mine shaft Canadian stuff? the trashy Mississippi stuff?) seemingly THC has strong anti-cancer properties that more than compensate for the carcinogens as demonstrated in the various studies. Smoking anything is bad for the lungs- vaping is the way to go!