Many factors, including the role of the cytochrome P450 system such as CYP3A4*1G, may influence the effectiveness of peptic ulcer treatment. The study aimed to describe the treatment outcomes and distribution of CYP3A4*1G genotype in children with peptic ulcers. A descriptive cross-sectional study, longitudinal follow-up before and after six weeks of treatment was conducted on 100 children with peptic ulcers from October 2022 to February 2024. Children with peptic ulcers without H. pylori infection had a higher rate of anemia, and pyloric and duodenal deformation, compatible with children with H. pylori. The ulcer healing rate was lower in children with deep peptic ulcers, excess eosinophils in mucosal biopsies, and poor therapeutic compliance. The distribution of CYP3A4*1/*1, CYP3A4*1/CYP3A4*1G, CYP3A4*1G/CYP3A4*1G in the study was 43.2%, 48.1%, and 8.6%, respectively, with no difference by gender. There were no difference in ulcer healing rates according to the presence of the CYP3A4*1G variant. In conclusion, the degree of peptic ulcer healing in children varies according to several characteristics. However, there were no difference in ulcer healing rates according to the presence of the CYP3A4*1G variant.