According to the current data over 12 million Polish citizens smoke tobacco, 40% of them are women. Maternal smoking in pregnancy significantly increases the rate of having a low-birthweight baby, the rate of perinatal mortality and several other adverse pregnancy outcomes. The aim of the study was to estimate the rate of smoking women during pregnancy and those who are exposed to secondhand smoke. 219 women hospitalized at Gynecology and Obstetrics Department of Wroclaw Medical University and Gynecology and Obstetrics Department in Opole have undergone the examination. The pregnant women have been interviewed and the results of questionnaire have been checked by the exhaled carbon monoxide (ExhCO) measurement. CO expresses the percentage of carboxyhemoglobin (HbCO) and is used for objective monitoring tobacco smoking. The results of the study suggest that regular exposure to secondhand smoke becomes a serious problem. 25.5% patients from Wrocław and 16.4% patients from Opole have declared passive smoking. The mean value of ExhCO in this group of women obtained the level of 3.3 ppm vs 1.95 ppm in the group of patients who have denied both active and passive exposure.