The aim was to investigate the characteristics of abdominal fat distribution in Japanese adolescents with type 2 diabetes mellitus.Eighty-six Japanese adolescents with simple obesity or type 2 diabetes mellitus treated between 2002 and 2018 were included. The subjects were classified into the simple obesity group (SO group, n=38) and type 2 diabetes mellitus group (DM group, n=23) by matching average age and gender ratio. The metabolic parameters VFA, SFA, and V/S ratio were compared between the 2 groups. Multivariate logistic regression analysis was performed to identify clinical factors associated with type 2 diabetes mellitus. Linear regression analysis was performed between hemoglobin A1c (HbA1c) and visceral fat area (VFA), subcutaneous fat area (SFA), or VFA-to-SFA ratio (V/S ratio) among all enrolled subjects. Finally, correlation analyses were performed to determine the relationships between VFA, SFA, and V/S ratio and metabolic parameters of the DM group. For the metabolic parameters, serum lipids, alanine aminotransferase (ALT), and HbA1c were measured without fasting. The VFA and SFA at umbilical level were investigated using computed tomography.VFA and V/S ratio in DM group were higher than those in SO group (p=0.04 and p<0.01, respectively). SFA in DM group was lower than that in SO group (p<0.01). VFA and SFA, and non-high density lipoprotein (HDL) cholesterol were identified as being independently associated with type 2 diabetes mellitus (odds ratio, 1.05, 0.98, and 1.04, respectively, p<0.05). HbA1c was correlated with VFA and V/S ratio (p<0.01). In DM group, VFA and SFA were positively correlated with systolic blood pressure (p<0.01), ALT (p<0.05), total cholesterol (p<0.05), and non-HDL cholesterol (p<0.01); however, V/S ratio was not correlated.Abdominal fat distribution in Japanese adolescents with type 2 diabetes mellitus was different from those with simple obesity and might associate with glucose and lipid metabolism.