To determine the extent and duration of breastfeeding in preterm and sick newborn infants admitted to a level IIb neonatal unit (NU). Hospital-based follow-up of 1730 infants born in 1996, 2001 and 2004, and studied from discharge to 6 months of post-natal age. At discharge from the NU, 98% of term (n = 945) and 92% of preterm (n = 785) infants were exclusively or partly breastfed. Exclusive breastfeeding increased at 2 months of corrected post-natal age and 78% of term infants were still exclusively or partly breastfed at 6 months of corrected post-natal age. Duration of breastfeeding among preterm infants was significantly shorter than in infants born at term. However, even among extremely preterm infants with a gestational age <28 weeks, 41% were still breastfeeding, exclusively or in part, at 6 months of post-natal age. There was no difference in breastfeeding after neonatal care in 1996 as compared to 2004. Moreover, the study showed that the breastfeeding after neonatal care differed only slightly from population data for all infants in Sweden. Breastfeeding can be successfully established in most preterm and previously sick neonates.