X-nuclei (13C, 31P, 19F etc) MRI and spectroscopy are of great interest since these methods provide a non-invasive technique to study in-vivo metabolite changes due to various diseases. To provide anatomical landmarks for interpretation of X-nuclei spectroscopic data, 1H anatomical images are required. To eliminate uncertainties associated with repositioning the patient, the RF coil must also resonate at the 1H frequency. This technique is called double-tuning (DT) of the RF coils. The choice of DT design is determined by the requirements of a specific application. Various methods of constructing DT RF surface coils, volume coils, and phased arrays are discussed.