There is provided a phantom for measuring a performance parameter of a nuclear magnetic resonance scanner capable of acquiring NMR data from a study object. The phantom is made up of a housing composed of a substantially non-NMR-active material, and positionable in use within a radio-frequency coil forming part of an NMR scanner. The phantom further includes a first medium disposed within the housing to load the radio frequency coil in a manner similar to that of a patient. The NMR properties of the medium are further selected such that an NMR signal, if any, produced by the medium occurs at a time other than when a performance parameter of said NMR scanner is measured. In the preferred embodiment, the phantom comprises two concentrically disposed cylinders of different diameters and a pair of end plates fastened to opposite ends of the cylinders. The first medium is disposed within the volume defined between the side walls of the cylinders and the end plates. A second medium is disposed within the volume defined within the innermost cylinder and generates the NMR test signals.