Significant progress has been made recently in the variety of ways that cancer can be non-invasively imaged in murine tumour models. The development and continued refinement of specialized hardware for an array of small animal imaging methodologies are only partly responsible. So too has been the development of new imaging techniques and materials that enable specific, highly sensitive and quantitative measurement of a wide range of tumour-related parameters. Included amongst these new materials are imaging probes that selectively accumulate in tumours, or that become activated by tumour-specific molecules in vivo. Other tumour imaging strategies have been developed that rely upon the detection of reporter transgene expression in vivo, and these too have made a significant impact on both the versatility and the specificity of tumour imaging in living mice. The biological implications resulting from these latest advances are presented here, with particular emphasis on those associated with MRI, PET, SPECT, BLI, and fluorescence-based imaging modalities. Taken together, these advances in tumour imaging are set to have a profound impact on our basic understanding of in vivo tumour biology and will radically alter the application of mouse tumour models in the laboratory.