Functional constipation is a prevalent problem in children. This study was designed to compare the efficacy and safety of molasses with polyethylene glycol (PEG) in childhood constipation. This randomized single-center trial was conducted in Amir Al-Momenin Hospital, Semnan, Iran. 110 constipated children aged from 2 to 8 years were randomly assigned to 2 g/kg PEG or 2 ccs/kg molasses. Children were treated for 1 month, and frequency of defecation, frequency of encopresis, abdominal pain, appetite, fecaloma, and pain at defecation were compared. The safety of both treatments was also studied. After 1 month of treatment, both drugs had an equal effect on the frequency of defecation and the frequency of encopresis per week (P <0.05). Both drugs were effective in relieving defecation pain to some extent. Molasses had a better effect on appetite status (P <0.05). Molasses caused a lower rate of side effects; diarrhea (P <0.01), nausea (P <0.05), and vomit. Our study showed that red sugar was as effective as PEG 3350 for treating childhood functional constipation. Manuscript profile