Wnt1-inducible signaling pathway protein-1 (WISP1), a member of the CCN family, is increasingly being recognized as a potential target for obesity and type 2 diabetes mellitus. Recent studies have shown that WISP1 can regulate low-grade inflammation in obese mice, and circulating WISP1 levels are associated with obesity and type 2 diabetes mellitus in adults. Herein, we measured serum WISP1 levels in obese youth and explored its relationships with pro-inflammatory cytokine interleukin 18 (IL-18) and other metabolic indexes. Totally, 44 normal-weight and 44 obese children and adolescents were enrolled. Physical and laboratory data were recorded, and then serum levels of WISP1 and IL-18 were determined by enzyme-linked immunosorbent assays. Results showed that serum levels of WISP1 were significantly higher in obese children and adolescents than in normal-weight healthy controls (1735.44 +/- 15.29 vs. 1364.08 +/- 18.69 pg/mL). WISP1 levels were significantly positively correlated with body mass index (BMI) and BMI z-score (r=0.392, P=0.008; r=0.474, P=0.001, respectively) in obese group; circulating IL-18 was increased in obese individuals (1229.06 +/- 29.42 vs. 295.87 +/- 13.30 pg/mL). Circulating WISP1 levels were significantly correlated with IL-18 (r=0.542, P<0.001), adiponectin (r=0.585, P<0.001) and leptin (r=0.592, P<0.001). The multivariate stepwise regression analysis showed that higher IL-18 levels represented the main determinant of increased WISP1 levels after adjusting for BMI, waist circumference, fasting insulin, homeostatic model assessment of insulin resistance (HOMA-IR) and HbA1c in obese individuals (=0.542, P=0.000). WISP1 can be involved in glucose/lipid metabolism in obese youth, which may be modulated by IL-18. Increased WISP1 levels may be a risk factor of obesity and insulin resistance, and WISP1 has a potential therapeutic effect on insulin resistance in obese children and adolescents.