Women who quit smoking during pregnancy gain more weight than women who continue to smoke. Concern about weight gain is a barrier to smoking cessation in the general population, but whether attitudes about weight are associated with failure to stop smoking during pregnancy or to maintain abstinence postpartum is unknown. Thus, attitudes about weight were assessed in 412 pregnant smokers recruited from obstetric practices in Massachusetts for a smoking cessation intervention trial. Smoking cessation outcomes (7-day point-prevalence abstinence by self-report and by cotinine-validation) were assessed at end-of-pregnancy and 3 months postpartum. Bivariate and multivariable analyses assessed the relationship between attitudes about weight and smoking cessation. In bivariate analyses, a high level of concern about post-cessation weight gain was associated with older age (p = .01), smoking more cigarettes/day (p<.001), not making a quit attempt in pregnancy (p = .02), being less likely to self-report tobacco abstinence at end of pregnancy (p = .01) and postpartum (p = .02), and having less cotinine-validated abstinence at 3 months postpartum (p = .05). In multivariable analyses that adjusted for cigarettes/day, a low level of concern about post-cessation weight gain was associated with more self-reported abstinence at end-of-pregnancy (OR = 1.77, 95% CI 1.01-3.09) and postpartum (OR = 2.09, 95% CI 1.05-4.14), but not with cotinine-validated abstinence at end-of-pregnancy (OR = 1.30, 95% CI 0.63-2.68) or postpartum (OR = 2.18, 95% CI 0.93-5.10). In conclusion, women who are more concerned about post-cessation weight gain may be less likely to quit smoking during pregnancy or remain abstinent in the postpartum period.