Being severely overweight is a distinctive clinical feature of Prader-Willi Syndrome (PWS). This explorative study aims to characterise balance capacity in PWS as compared to non-genetically obese patients (O) and to a group of normal-weight individuals (CG). We enrolled 14 PWS patients: 8 females and 6 males (BMI = 41.3 [plus or minus] 7.3 kg/m[squared], age = 32.86 [plus or minus] 4.42 years), 44 obese individuals, 22 males and 22 females (BMI = 40.6 [plus or minus] 4.6 kg/m[squared], age = 34.2 [plus or minus] 10.7 years) and 20 controls (CG: 10 females and 10 males; BMI: 21.6 [plus or minus] 1.6 kg/m[squared]; age: 30.5 [plus or minus] 5.3 years). Postural acquisitions were conducted by means of a force platform from which the COP pattern vs time was analysed. The participants were required to stand barefoot on the platform with eyes open and heels at standardized distance and position for 60 s. All of the analysed parameters were statistically different from O and CG groups. PWS individuals showed greater displacements in both the A/P and M/L direction (RMS, RANGE and MV indices). Analysis of the overall planar movement of the CoP showed that the PWS patients were characterised by higher RMS distance from the centre (RMS[subscript CoP] index) and area of confidence ellipse (AREA[subscript CoP] index) when compared both to obese and healthy individuals. PWS patients showed a poorer balance capacity than their non-genetically obese counterparts and healthy individuals, with greater differences in both the A/P and M/L direction than O. Rehabilitation programs for PWS should take this finding into account. In addition to weight loss, strengthening of ankle flexors/extensors, and balance training, tailored interventions aimed at improving A/P control should be given particular consideration. (Contains 1 table.)