The high sensitivity and spatio-temporal resolution of positron emission tomography (PET) makes this non-invasive imaging technique ideal for the in vivo tracking of liposomal nanomedicines in the clinical setting. This image-guided therapeutic approach may eventually allow selection of patients that would benefit from the nanomedicinal treatment and, by doing so, enhance the clinical value/efficacy of this promising treatment. In this chapter, we review the different methods reported to date of radiolabel liposomal nanomedicines with PET isotopes such as ⁸⁹Zr, ⁶⁴Cu and ¹⁸F and discuss their advantages and limitations for clinical translation.