A dietary interview performed by expert personnel is the best method to check whether patients with coeliac disease follow a strict gluten-free diet (GFD). We previously developed a score based on four fast and simple questions that can be administered even by non-expert personnel. The aim of the present study is to verify the reliability of our questionnaire in a new cohort of patients. The questionnaire has a five-level score. From March 2008 to January 2011, the questionnaire was administered to 141 coeliac patients on a GFD, who were undergoing re-evaluation. The score obtained was compared with persistence of both villous atrophy and endomysial antibodies (EMA). The rate of lower scores was higher among the patients with persistence of either villous atrophy (Fisher's exact, P < 0·001; test for trend, P < 0·001) or positive EMA (Fisher's exact, P = 0·001; test for trend, P = 0·018). Given that the coeliac patients have been well instructed on what a GFD means and on how to follow it, our questionnaire is a reliable and simple method to verify compliance to a GFD.