Many epidemiological studies support a relationship between maternal smoking during pregnancy and adverse neurobehavioral effects later in life. Prenatal exposure to tobacco seems to increase the risks for cognitive deficits, attention deficit/hyperactivity disorder, conduct disorder, criminality in adulthood and a predisposition in the offspring to start smoking and alcohol abuse. Nicotine readily crosses the placenta and the fetuses of mothers who smoke are exposed to relatively higher nicotine concentrations than their mothers. In the fetal brain nicotine can activate nicotinic receptors which play an important role during development of the brain. A direct specific action on the developing human brain is plausible during the major part of the prenatal life, since the nicotinic receptors are already present in the brain during the first trimester.