Abstract Purpose: We evaluated the efficacy and safety of combined oral and enema therapy using polyethylene glycol 3350 with electrolyte solution for disimpaction in hospitalized children. Methods: We retrospectively studied 28 children having functional constipation who received inpatient treatment between 2008 and 2016. The amount of oral polyethylene glycol ( PEG) 3350 electrolyte solution administered was 50-70 mL/kg/day ( PEG 3350, 3-4.1 g/kg), and an enema solution was administered 1-2 times a day as a single dose of 15-25 mL/kg ( PEG 3350, 0.975-1.625 g/kg). A colon transit time (CTT) test, based on the Metcalf protocol was performed in some patients. Results: Administration of oral and enema doses of PEG 3350 electrolyte solution showed 2.1 ± 0.3 times and 2.9 ± 0.4 times, respectively. After disimpaction, the frequency of defecation increased from 2.2 ± 0.3 per week to once a day (1.1 ± 0.1 per day). The number of patients who complained of abdominal pain was reduced from 15 (53.6%) to 4 (14.2%). Before hospitalization, nine patients underwent a CTT test, and 5/9 patients (62.5%) were classified as belonging to a group showing abnormalities. And in some patients, mild adverse effects were noted. We examined electrolytes and osmolality before and after disimpaction in 16/28 patients, and no abnormalities were noted. Conclusion: In terms of therapeutic efficacy and safety, combined oral and enema therapy using high-dose PEG 3350 with electrolytes is considered superior to conventional oral monotherapy or combined oral and enema therapy on an outpatient basis.