Chitotriosidase (ChT) is an enzyme secreted by activated macrophages and involved in defense against, and in degradation of chitin-containing pathogens, such as fungi, nematodes, and insects. In addition, it plays an important role in the development of atherosclerosis related with systemic low-grade inflammation. To this effect of activity of ChT, we aimed to investigate serum ChT activity in obese subjects and to determine to relation with insulin resistance and high-sensitive C-reactive protein (hsCRP). A total of 73 obese subjects (10.9+/-2.6 years of age, 44 male patients) and 41 age and gender-matched healthy lean subjects (11.6+/-2.9 years of age, 18 male patients) were included in this study, between 2007 and 2008. The criterion for diagnosing obesity was defined as the body mass index (BMI) being over 97th percentile of the same gender and age. Fasting serum glucose, insulin, hsCRP and ChT levels were measured. We compared the differences in variables between obese and lean subjects with Student's t-test compared after ascertaining that the data were normally distributed. All data were expressed as mean+/-standard deviation. There was statistically significant increase in serum ChT activity of obese subjects, while there was statistically significant difference in serum hsCRP levels when compared to healthy lean subjects (30.0+/-17.9 and 23.0+/-17.8, p = 0.045; 2.3+/-3.1 and 0.7+/-1.2, p = 0.001). Obese subjects had significantly higher BMI-SDS, TG and HOMA-IR and lower HDL-C levels when compared with the healthy lean subjects (p < 0.05). Correlation analysis showed no significant correlation between serum ChT activity and hsCRP, HOMA-IR and BMI-SDS (p > 0.05). Although the data need to be validated by further investigation, the observations made in this study seem to indicate that serum ChT activity may not be a useful marker for monitoring systemic low-grade inflammation and insulin resistance in obese subjects.