Recent studies have suggested that the reflux of gastric contents can cause adenoid hypertrophy (AH). The frequency of gastro-oesophageal reflux disease (GERD) in this AH population is unknown, but according to studies using pH-metry it may be as high as 65%. The aim of this study was to estimate the frequency of GERD among children with AH.This was a cross-sectional, multicentre, prospective study of children with AH selected for adenoidectomy. The diagnosis of AH was made by a single laryngologist using a flexible fiberscope. All children had 24-hr multichannel intraluminal pH-impedance (MII/pH) assessment. A GERD diagnosis was made using BioVIEW software analysis after manual review by a single investigator.38 consecutive patients (21 males, mean age 6.58 years) were enrolled in the study. GERD was diagnosed in 5 (13.2%) patients. A total of 1462 gastro-oesophageal reflux events (GERs) were detected by MII/pH and the majority (60.9%) were acidic. The only significant differences between the GERD-positive and GERD-negative groups were the total number of GERs, and the number of acid GERs.It is first study using MII/pH to assess the frequency of GERD in children with AH. The data suggest that GERD in children with AH seems to be not as common as it was previously raised. Further studies are needed to confirm these results.