Background: The gold standard of glycemic control index in diabetes management glycated hemoglobin(HbA1c) concentration has limitations in the assessment of daily glycemic excursion. Recent studies suggest that serum 1,5-anhydroglucitol(1,5-AG) level as a reflection of short-term glucose status, postprandial hyperglycemia, and glycemic variability which are not captured by HbA1c. Aim: The aim of this study was to investigate the usefulness of 1,5-AG in children and adolescents with obesity or diabetes. Methods: A retrospective medical record of forty children and adolescents aged 8 to 20 years (24 girls an 16 boys) who had 1,5 AG data were obtained between August 2011 and July 2014 at Konkuk university medical center. Subjects were classified into two group, diabetes and obesity. Results: 1,5-AG levels were lower (4.8짹5.0 vs.32.1짹10.0 µg/mL, p0.0001) and HbA1c levels were higher (10.7짹2.9 vs. 5.5짹0.3, p0.0001) in diabetes compared to obesity. Negative correlation between 1,5 AG and HbA1c was significant (r=-0.767, p0.0001). The range of 1,5-AG level of obese children was wide (19~59.3 µg/mL) and was not predicted by HbA1c. 1,5 AG and HbA1c relationship was not significant in diabetes group. For HbA1c 5.5-8.0%, 1,5-AG was significantly correlated with HbA1c (r= -0.844, p0.0001). Coclusions: 1,5-AG might be a reliable index in mid-term assessment of obese children with HbA1c 竊�5.5% and diabetes patient with HbA1c8%, beyond that provided by HbA1c regarding hyperglycemia and glycemic excursions.