AbstractBackgroundAdherence to Helicobacter pylori (H. pylori) eradication treatment is a cornerstone for achieving adequate treatment efficacy.ObjectiveTo determine which factors influence compliance with treatment.MethodsA systematic prospective non‐interventional registry (Hp‐EuReg) of the clinical practice of European gastroenterologists. Compliance was considered adequate if ≥90% drug intake. Data were collected until September 2021 using the AEG‐REDCap e‐CRF and were subjected to quality control. Modified intention‐to‐treat analyses were performed. Multivariate analysis carried out the factors associated with the effectiveness of treatment and compliance.ResultsCompliance was inadequate in 646 (1.7%) of 38,698 patients. The non‐compliance rate was higher in patients prescribed longer regimens (10‐, 14‐days) and rescue treatments, patients with uninvestigated dyspepsia/functional dyspepsia, and patients reporting adverse effects. Prevalence of non‐adherence was lower for first‐line treatment than for rescue treatment (1.5% vs. 2.2%; p < 0.001). Differences in non‐adherence in the three most frequent first‐line treatments were shown: 1.1% with proton pump inhibitor + clarithromycin + amoxicillin; 2.3% with proton pump inhibitor clarithromycin amoxicillin metronidazole; and 1.8% with bismuth quadruple therapy. These treatments were significantly more effective in compliant than in non‐compliant patients: 86% versus 44%, 90% versus 71%, and 93% versus 64%, respectively (p < 0.001). In the multivariate analysis, the variable most significantly associated with higher effectiveness was adequate compliance (odds ratio, 6.3 [95%CI, 5.2–7.7]; p < 0.001).ConclusionsCompliance with Helicobacter pylori eradication treatment is very good. Factors associated with poor compliance include uninvestigated/functional dyspepsia, rescue‐treatment, prolonged treatment regimens, the presence of adverse events, and the use of non‐bismuth sequential and concomitant treatment. Adequate treatment compliance was the variable most closely associated with successful eradication.