A serological test for the diagnosis of Helicobacter pylori infection (Cobas Core Roche, IgG, 2nd Generation; Roche, France) was compared with the examination of biopsy samples (culture and histology) obtained after endoscopy in 115 children to assess its value. In 94 children (42 positive and 52 negative), results were concordant. In 10 children a positive serological test was associated with an absence of Helicobacter pylori, while in 11 others a negative serological test was associated with a positive culture. Sensitivity of the test was 79.2% and specificity 83.9%. A relationship between IgG titers and age (r = 0.31, p < 0.05) was found. Serological tests could be useful for the diagnosis of Helicobacter pylori infection, but a negative test result does not rule out infection, particularly in children under 10 years of age.