Dendrimers are dendritic or branched polymers that can be synthesised to provide macromolecular constructs with hydrodynamic radii in the low nanometer size range and with good control over size and surface properties. As such dendrimers show increasing promise as drug delivery vectors, and have particular application in cancer therapy. In common with most potential nanomedicines, the in vivo distribution properties of dendrimers are highly dependent on molecular weight and surface character. Derivatisation of the dendrimer surface with polyethylene glycol (PEG), for example, can maintain concentrations of dendrimer based drug delivery systems in the plasma for several days and in doing so promote passive uptake into sites with increased vascular permeability. PEGylation also promotes absorption from subcutaneous injection sites and appears to preferentially redirect a proportion of the administered dose into the lymphatics and lymph nodes. These delivery properties are highly consistent with the use of dendrimers as drug delivery vehicles and when coupled with the use of tumour-specific drug release mechanisms have the potential to significantly enhance therapeutic benefit. Here, the impact of modification of the dendrimer surface with a PEG on dendrimer absorption, clearance and tumour targeting is described and the implications of these findings for delivery system design discussed. Examples of PEGylated and drug conjugated dendrimers as enhanced anti-cancer nanomedicines will be subsequently described and in particular recent data suggesting utility in the targeted treatment of lymph-resident and lung-resident cancer metastases.