The most common Melanocortin-4 receptor (MC4R) missense variant Val103Ileu (rs2229616) is related to obesity. In this study, we examined the distribution of MC4R polymorphisms both in the clinical pediatric obese group and in the high/lowsocioeconomic school group. 24 probable exogene obese children without family history (group I), 66 probable familial obese children (group II), and 111 complicated obese children (group III) were included. Groups I and II obese participants were gathered in a school-based epidemiologic study and compared with 49 apparently healthy non-obese controls. Significant difference in genotype distribution was observed between the groups I and II. Val 103 Ile polymorphism was more common among group III (4.5%). Furthermore, we detected Glu 42 Lys (18.18%) polymorphism in our population, which was not previously reported. Frequency of Val 103 Ile (A) allele polymorphism was 0.75 and 2.25; Glu 42 Lys A allele polymorphism was 9.0 and 1.5, in groups II and III, respectively. None of the MC4R mutations were found in high-socioeconomic school and in control groups. Our data indicated that MC4R polymorphisms were more frequent both in clinical pediatric obese group and in low-socioeconomic school group. In addition, our data revealed that carrying the polymorphism may increase the hereditary form of obesity.