Background: In Poland, prenatal exposure to tobacco smoke is observed in about 30 percent of children and postnatal in over 50 percent of children. This exposure has serious health consequences, including the negative effect on child neurodevelopment. The aim of the study was to assess the effect of environmental tobacco smoke (ETS) exposure on child psychomotor development. Material and methods: The study population consisted of 63 children with well assessed prenatal ETS exposure (a threefold analysis of cotinine level in saliva of pregnant women). To assess ETS exposure in infants within one year after birth a questionnaire-based interview was conducted with mothers. The Bayley Scale for Infant and Toddler Development (BESID-III) was used for the evaluation of child neurodevelopment. Results: Multivariate analysis (including gender, birth order of the child and parental educational status) indicated the statistically significant association between prenatal exposure to ETS and cognitive child development (b = -4.0; p = 0.04). ETS exposure has also a negative impact on motor (b = -2.7; p = 0.2) and language (b = -3.4; p = 0.08) abilities of the child although the results were not statistically signifi cant. Conclusions: Maternal smoking was found to be related to a decrease in child neurodevelopment, however, it was impossible to separate the prenatal from postnatal exposure. A lot of effort should be made to eliminate ETS exposure of children. Med Pr 2009;60(1):15-20