It was reported recently that body mass index (BMI) is a prognostic factor of vascular complications after radial puncture, and that extremely thin patients are at higher risk than obese subjects. However, the underlining mechanism of this phenomenon has rarely been studied. Therefore, we conducted a survey measuring a novel parameter, the skin fold thickness, and other potential risk factors in our patients developing postprocedure hematoma. In 1176 consecutive patients undergoing percutaneous radial catheterization, 18 (1.53%) developed hematoma afterward. When a patient with hematoma had been identified, the next patient having no hematoma after radial puncture was enrolled into the control group, which thus turned out to have 18 patients. In addition, we also compared the BMI, skin fold thickness, and other potential risk factors, including heparin dosage and antiplatelet medication, between these 2 groups. We found hematoma patients to be older (69.5 +/- 10.3 years vs 61.50 +/- 11.7 years, P = .037), to have more cases of coronary intervention (10/18 vs 4/18, P = .04), to have lower BMI (23.63 +/- 4.03 vs 27.25 +/- 4.38, P = .014), and to have thinner skin folds of forearm (5.94 +/- 4.56 vs 9.27 +/- 3.06 mm, P = .015), deltoid area (14.61 +/- 9.00 vs 19.73 +/- 7.15 mm, P = .042), and waist (21.94 +/- 9.90 vs 29.00 +/- 8.46 mm, P = .028) than the nonhematoma group. On the contrary, no statistical difference in heparin dosage or other factors was noted between the 2 groups. We conclude that the vascular complication rate after radial catheterization is higher in elderly patients with lower BMI, body weight, or thinner skin folds.