Nanoparticle formulations offer alternatives to viral vectors for the delivery of genes, siRNAs and other oligonucleotides for therapy of a range of genetic diseases, cancers and diseases of aging. However, to date, gene and siRNA therapies with non-viral formulations, despite exhaustive efforts, have made little headway towards clinical efficacy or pharmaceutical products. Many nanoparticle formulations have been reported to display great promise in cell culture studies but their efficacy often fails to translate to in vivo models. Imaging of nanoparticles enables close-to real time imaging of nanoparticle biodistribution which can have a great impact on transfection efficacy. This talk will focus on methods of labelling and detecting nanoparticles by imaging techniques to monitor their biodistribution for treating diseases of lung, brain and tumours.