Purpose: The objective of the present study was to assess the persistence of non-nutritive sucking habits and its relationship with breastfeeding, as well as to establish the influence of sociodemographic factors on these habits among children aged 3 to 5 years. Materials and Methods: A case-control study was conducted with 1107 children from public and private daycare centres in Natal, Brazil: 450 in the case group (312 pacifier suckers and 138 thumb suckers) and 657 in the control group (habitfree). Data regarding sociodemographic conditions and duration of breastfeeding were obtained using a structured questionnaire. Results: Breastfeeding for a duration of > 6 months (adjusted odds ratio = 0.311; 95% confidence interval = 0.226 to 0.428) was an independent protective factor against persistent pacifier sucking. The use of pacifiers was more frequent among 3-year-old children and among those from a higher income family and a higher level of schooling of parents. The relation between duration of breastfeeding and thumb sucking was not statistically significant (P = 0.087). There was an association between the thumb sucking habit with sex (female), low level of schooling of father and the child being born as the last male child in the birth order. No relation was found between breastfeeding and habit frequency (day/night and night) (P = 0.301). An association with habit frequency was found with the age of 3 years, female, the family income group that ranged between US $176 and US $875, and those attending private institutions. Conclusions: Breastfeeding for a duration of > 6 months was a protective factor against the persistence of pacifier sucking, but the subjectivity of the mother-child relationship must be investigated further. Parole chiave: bottle-feeding, breastfeeding, sucking habits