Smoking appears to be one of the most significant risk factors in the development and progression of periodontal disease. Smoking is also a risk factor in the development of peripheral vascular diseases. Blood vessels in smokers are fewer and are subjected to stenosis. Clinically, it is well known that bleeding on probing, gingival exudates and redness and swelling in gingival sites of smokers are less than in non-smokers. According to previous studies, there is a relative increase in gingival blood flow immediately after smoking, while gingival blood flow itself is considerably decreased in healthy smokers in comparison with non-smokers. In this investigation, we used laser Doppler flowmetry to study gingival microcirculation in smokers with light, moderate and heavy periodontitis in comparison with non-smokers with the same diseases. Our results show, that smoking decreases gingival blood flow in smokers with periodontitis comparing to non-smokers with periodontitis. Immediately after smoking there is an increase in gingival microcirculation. In 30 minutes we observed a marked decrease in gingival blood flow in all groups, followed by gradual restoration of blood flow rate, registered before smoking. This restoration took 1.5-2 hrs in group with light periodontitis, 2 hrs in group with moderate periodontitis and more than 2 hrs in group with heavy periodontitis. We suppose, that constant changes in blood supply of periodontal tissue caused by smoking may contribute to higher prevalence and faster progression of inflammatory periodontal diseases in smokers.