To quantify the moulding ability of Plaster of Paris and polyester cast materials as assessed by the novel use of peripheral quantitative computed tomography. A prospective crossover study was performed in 25 healthy volunteers aged 18–65 years. Participants’ non-dominant wrist was immobilized using a synthetic polyester cast followed by a Plaster of Paris cast with three point moulding to simulate reduction of a dorsally angulated distal radius fracture. The novel use of peripheral quantitative computed tomography was used to measure the closeness of fit of each cast on an axial tomographic slice. Plaster of Paris casts were able to achieve a closer mould than polyester when measured between the bone and the cast (p=0.002), as well as between the skin and the cast (p=0.001). There was no difference when stratified on BMI. Using pQCT assessment, a closely moulded fit was able to be more consistently achieved when using Plaster of Paris when compared to polyester casts of the distal radius. III.