Patterns and correlates of maternal smoking could differ according to ethnic background, and these differences might have consequences for intervention strategies. In the Generation R study, we examined patterns of smoking during pregnancy and the associations of socioeconomic (educational level), demographic (maternal age, marital status, generational status, parity) and lifestyle (alcohol consumption, partner smoking) correlates with smoking during pregnancy in 5,748 women of Dutch, Turkish, Moroccan, Surinamese-Hindustani, Surinamese-Creole, Capeverdean and Antillean ethnic background. Smoking rates before pregnancy were highest in the Turkish group (43.7%) and lowest in the Moroccan group (7.0%). Compared with Dutch women (24.1%), Turkish and Moroccan women were less likely to quit smoking before pregnancy (17.0% and 5.9%, respectively; p <.001). Turkish and Moroccan women (72.0% and 70.6%, respectively) were more likely to continue smoking during pregnancy compared to Dutch women (58.6%, p <.001). Lower education was associated with smoking during pregnancy only in the Dutch group. No significant association of education with smoking was seen in the non-Dutch groups. Second-generation (i.e., foreign-born) Turkish and Capeverdean women were more likely to smoke during pregnancy compared with first-generation women. Partner smoking was associated with smoking during pregnancy in all ethnic groups except for Surinamese-Creole and Antillean. Maternal alcohol consumption was associated with smoking during pregnancy in all ethnic groups except for Capeverdean. Smoking rates and correlates of smoking during pregnancy varied by ethnic background. These observations should be considered when designing maternal smoking prevention and intervention strategies.