Background/aims: Functional constipation and gastroesophageal reflux disease are two major and commonly encountered components of childhood functional gastrointestinal disorders. Epidemiological studies in, the adult population support that there is a significant overlap between the different functional disorders of the digestive tract. Therefore, we aimed to investigate the frequency of gastroesophageal reflux disease in children with functional constipation and to compare clinical findings and 24-h esophageal pH monitoring with a group of patients with suspected gastroesophageal reflux disease. Materials and Methods: Children between 4 and 16 years old with functional constipation (based on Rome III criteria, Group 1; n=38) were prospectively evaluated. A control group was composed of patients with symptoms suggesting gastroesophageal reflux disease (Group 2; n= 40). All patients included in the study were asked about reflux-related symptoms, and then all cases underwent 24-h esophageal pH monitoring analysis. Results: Delayed gastric emptying symptoms such as belching and hiccups were more common in patients in. Group 1 (p=0.002, p=0.021, respectively), whereas chronic cough was more common in patients in Group 2 (p=0.012). According to the 24-h esophageal pH monitoring, pathologic acid reflux in the lower and/or laryngopharyngeal portion of the esophagus was determined in 39.5% of the patients in Group 1 and in 42.5% of the patients in Group 2 (p=0.96). No significant difference was found in terms of age, gender and duration of constipation in patients with and without acid reflux in Group 1 patients. Pyrosis (66.6 vs. 0%, p=0.00001) was more common in Group 1 patients with acid reflux, but hiccups (20 vs. 69.5%, p=0.007) and belching (33.3 vs. 60.8%, p=0.184) were more common in patients in Group 1 without acid reflux. Conclusions: Gastroesophageal reflux disease should be considered in the treatment and monitoring of patients with functional constipation. Further studies are needed using 24-h pH multi-channel impedance.