INTRODUCTION: Clinical questionnaires have some limitations compared to instrumental diagnosis of gastroesophageal reflux disease (GERD), but clinical diagnosis of GERD based on typical symptoms is pragmatic and well-established by societal guidelines. AIM: To study the diagnostic value and provide comparative analysis of GerdQ and GSRS questionnaires regarding the GERD diagnostics based on a comparison of the questionnaires with the results of intraluminal oesophageal impedance-pH monitoring in Ukraine. MATERIAL AND METHODS: Twenty-eight patients (11 men and 17 women with a mean age of 47 ±2.4 years and a mean body mass index of 25.6 ±1.1 kg) filled in the GerdQ and GSRS questionnaires and underwent 24-hour multichannel intraluminal oesophageal impedance-pH monitoring. RESULTS: The GerdQ questionnaire showed a significantly strong correlation between the total score of the questionnaire and the key indicators of 24-hour impedance-pH monitoring: AET ( = 0.793), acid reflux episodes ( = 0.796), and liquid reflux episodes ( = 0.730). Correlation of reflux syndrome according to the GSRS questionnaire was established between the acid reflux episodes ( = 0.530), the episodes of all fluid refluxes ( = 0.598), and AET ( = 0.560), but the strength of the correlation relationships is weaker. The GerdQ questionnaire showed a sensitivity of 78.6%, specificity of 92.9%, and accuracy (diagnostic efficiency) of 85.7%. CONCLUSIONS: The use of the GerdQ questionnaire for the diagnosis of GERD is optimal in everyday practice for deciding whether to prescribe "ex juvantibus" therapy or whether to use instrumental examination methods (upper endoscopy, oesophageal pH monitoring, oesophageal impedance-pH monitoring).