This multicenter, prospective, randomized, controlled trial will be conducted on 120 infants-children with a diagnosis of chronic functional constipation according to the definition of Criteria of Rome III. The enrolled subjects will be randomized according to an electronically generated randomization list in 2 groups: one group will receive micro-enemas of Promelaxin® (Group A) while the second group will receive Macrogol 4000 per os (Group B) . Children will receive the dedicated treatment for two weeks and then undergo a follow-up period of a maximun of 6 weeks.