INTRODUCTION: Gastroesophageal reflux disease (GERD) is a very common disorder that substantially affects the patient's quality of life. AIM: Our aim was to detect the frequency of GERD in patients with hiatal hernia (HH), to compare the acid reflux pattern in patients with and without HH, and to search the relationship between the erosive gastroesophageal reflux (GER) and HH. METHODS: Forty patients with HH diagnosed by at least two methods, and 121 patients with GERD as a control group were studied. The frequency of GERD in patients with HH, the acid reflux pattern, the relation of body mass index and erosive esophagitis with HH and control group was studied. RESULTS: Among patients with HH 67.5% of patients had GER. On comparison of acid reflux pattern, the isolated distal esophageal reflux was seen more in patients with HH than in the control group (P < 0.0001). Erosive GERD was seen more in patients with HH than in the control group (P = 0.017). There was no difference in body mass indices between patients with HH and erosive gastroesophageal reflux disease and patients with HH and non-erosive GERD. CONCLUSION: Hiatal hernia is very closely associated with GERD, and isolated distal esophageal reflux is seen more in patients with HH than in patients without HH. There is no effect of body mass index on GER in patients with HH.