As a first-line therapy for Helicobacter pylori, dual therapy with vonoprazan and amoxicillin (VA-dual) provides an eradication rate similar to that of vonoprazan-based triple therapy. As the factors associated with the eradication rate of H. pylori with VA-dual are unknown,we investigated them in this study. Overall, 163 patients diagnosed with H. pylori infection received VA-dual (vonoprazan 20mg twice daily and amoxicillin 750mg twice daily for 7 d). The association between successful H. pylori eradication and the following patient clinical factors was analyzed: sex, age, height, weight, body surface area (BSA), body mass index (BMI), history of early gastric carcinoma and peptic ulcer, comorbidity of cirrhosis, alcohol consumption habit, smoking habit, common use of proton pump inhibitors, and concomitant use of drugs that are substratesof cytochrome P450 (CYP) 3A4. The association between post-eradication adverse events and clinical factors was analyzed retrospectively. Successful H. pylori eradication was associated with a lower BSA (eradication rate: 90.8% in patients with BSA <1.723 vs. 79.6% in those with BSA ≥1.723; p=0.045). The incidence of adverse events was higher in women than in men (adverse events: 40.0% in women vs. 19.4% in men; p=0.004). Successful H. pylori eradication with VA-dual was associated with the small body size of patients. This therapy may have to be adjusted per body size.