Over the past 20 years, numerous investigations have demonstrated epidemiologically and biologically that smoking is one of the most significant risk factors with respect to the development and progression of periodontal disease. In terms of the mechanism via which smoking influences periodontitis progression, various factors contribute to the deleterious periodontal effects of smoking, including alteration of both microbial and host response factors. Furthermore, since it is well known that smoking is also a risk factor of osteoporosis, the combination of smoking with osteoporosis further enhances the risk of periodontal disease. Recent investigations reported that passive smoking exposure may be a risk factor of periodontal disease and may stimulate inflammatory responses of periodontal tissue.