Introduction. The 210 Polonium 210 (210Po) is included among over 4,000 substances which are in the tobacco smoke; it's a well-known, often not recognized or underestimated alpha-sender. At the cigarette fire point (600 - 880°C), 210Po volatilizes and is inhaled free and partly through the corpuscular component which is mainly at the level of bronchial bifurcations.

Objects, materials and methods. We have searched for the possible presence of any kind of radioactivity in not smoked tobacco of five known brands of cigarettes and the only alpha radioactivity in smoked tobacco.

We have noticed:

1. traces of several radioactive substances (137Cs, 134Cs, 40K, 208TI, 228Ac, 212Bi, 212Pb, 214Bi, 214Pb e 226Ra) in not smoked tobacco;
2. the only 210Polonium expressed in mBq has been searched and identified in smoked tobacco;for each cigarette it was present in 75 mBq and subdivided like this:

- ash 68.8 mBq (91.7%)

- passive smoke (sidestream) 1.2 mBq (1.6%)

- active smoke (mainstream) 5 mBq (6.7%).

Conclusion. Our study has proved that:

1. at the cigarette fire point (600 - 880°C), 210Po is present both in the active smoke (mainstream) inhaled in the bronchopulmonary apparatus at 6.7% of the entire 210Po contained in the cigarettes, and in the outer environment where there are concentrations of 91.7% (ash) and 1.6% (sidestream);
2. 210Po presents an important pulmonary "pure" risk as initiator of bronchopulmonary tumor caused by alpha radioactivity (four cases out of 10,000 smokers a year), without considering the role of (cocarcinogen) promoter in bronchopulmonary tumor through a comprehensive synergic action with other tumorigenic substances.