OBJECTIVES The aim of the randomized trial was to evaluate the risk of smoking relapse one year after delivery among the women who quit smoking during pregnancy. MATERIALS AND METHODS The study was carried out in 2002 and 2003 and included the collection of data on smoking relapse within one year after delivery among 175 women who participated in the randomized smoking cessation trial and quit smoking during pregnancy. RESULTS About 50% of women who quit smoking during pregnancy relapsed into that habit within 12 months postpartum. The analysis of women who quit smoking before 14 weeks of pregnancy revealed a significantly higher risk of smoking relapse after delivery for women with the higher level of smoking addiction indicated by the Fagerström test (OR = 5.0; 95% CI: 1.5-16.2). Compared to the control group, spontaneous quitters who participated in intervention activities during pregnancy showed lower risk of smoking relapse within one year after giving birth (OR = 0.3; 95% CI: 0.1-0.9). In the group of women who quit smoking after 14 weeks of gestation, the risk of smoking relapse postpartum was significantly higher for those with the higher Fagerström test score (OR = 4.8; 95% CI: 1.6-14.1). The risk of smoking relapse 12 months after delivery was lower for spontaneous quitters who participated in the intervention during pregnancy and for women who quit smoking after participation in the intervention activities than for controls (OR = 0.03; 95% CI: 0.01-0.2, OR = 0.1; 95% CI: 0.03-0.6). CONCLUSIONS Women who had higher score in the Fagerström test before quitting smoking had significantly higher risk of smoking relapse within 12 months after delivery. Anti-smoking intervention during pregnancy helps women to maintain smoking abstinence after delivery.