Background: According to previous studies, patient with metabolic syndrome (MetS) are different in terms of body composition from healthy subjects. The purpose of the present study was to determine the body composition of healthy obese/overweight patients and compared them with those having MetS. Methods: A case-control study was conducted on both men and women aged 20 to 55 years, who were selected using sequential sampling method, based on the inclusion and exclusion criteria, from those referred to an endocrinology and the diabetes clinic affiliated to Tehran University of Medical Sciences. One hundred and forty seven subjects were enrolled in the study and divided into three groups, including 49 with MetS, 49 obese/overweight subjects without MetS, and 49 were normal weight subjects. Body composition was measured for all subjects using bioelectrical impedance analysis. NCEP ATP III was the criterion for definition of Mets. Results: No significant differences were found between the study groups in terms of demographic variables. The mean of the waist circumference (WC) was higher in MetS patients (P < 0.05) as compared with the control groups. Obese/overweight group had higher percentage of body fat and lower fat free mass than normal weight group (P < 0.05). Conclusion: Obese/overweight patients with and without MetS had significantly higher fat mass and WC than normal weight controls, while only WC was higher in MetS group as compared with obese/overweight patients without MetS. Therefore, reduction in body fat and WC should be emphasized in patients with MetS.