Not the vaping most people are thinking of but vaping cannabis oils that are made from clean extraction methods such as supercritical CO2, are logically much healthier for the lungs compared to smoking buds.
As for the trendy vape juice stuff that is not made from cannabis, I don't know. I would venture to guess it depends on what additives they put in the juice. I heard some juice has nasty shit in it like diacetyl which should be a crime. That stuff is known to cause bronchiolitis obliterans - an irreversible and progressive lung disease. So any of you vapers out there might want to read this
http://ehp.niehs.nih.gov/15-10185./