Background: Cigarette smoking during pregnancy increases the risk of adverse pregnancy outcomes and women who quit smoking at this time are able to reduce the risk of low birth weight, preterm labour, spontaneous abortion and perinatal death. This study investigates the sociodemographic characteristics of pregnant women who stop smoking during pregnancy and the association between stopping smoking and breastfeeding duration.Methods: A 12 month longitudinal study was conducted in two public maternity hospitals in Perth, Australia between mid-September 2002 and mid-July 2003. While in hospital, participating mothers completed a self-administered baseline questionnaire. Follow up telephone interviews were conducted at 4, 10, 16, 22, 32, 40 and 52 weeks.Results: A total of 587 (55%) mothers participated in the study. Two hundred and twenty six (39%) mothers reported smoking prior to pregnancy and 77 (34%) of these stopped smoking during pregnancy. Women who were pregnant for the first time were twice as likely ( OR = 2.05; 95% CI 1.047 - 4.03; p < 0.05) to quit smoking as multiparous women. Women who smoked more than 10 cigarettes per day were significantly less likely to quit smoking during pregnancy ( OR = 0.36; 95% CI 0.18 - 0.69; p < 0.05). Women who consumed alcohol before pregnancy were three times more likely to quit smoking ( OR = 2.58; 95% CI 1.00 - 6.66; p < 0.05). Quitting smoking during pregnancy was significantly associated with breastfeeding for longer than six months ( OR = 3.70; 95% CI 1.55 - 8.83; p < 0.05).Conclusion: Pregnancy is a time when many women are motivated to quit smoking and providing targeted smoking cessation interventions at this time, which take into account factors predictive of quitting smoking, are more likely to be successful.