The detection of biologically important molecules such as proteins and nucleic acids is of high and growing interest in the diagnosis of diseases from cancer to infectious and cardiovascular disease. The use of nanostructures to enhance sensitivity in biomolecular detection has now been reported in a broad range of assays. Here we provide direct evidence that the display of nucleic acid probe molecules on a nanostructured surface dramatically enhances hybridization efficiency compared to the case of the same probe molecules tethered on a smoother surface. Another factor expected to influence hybridization is the density of the probe monolayer. Remarkably, we find herein that the effect of nanostructuring dominates over probe density: the benefits of a high degree of nanostructuring can more than overcome the influence of dense probe packing. The results obtained herein give guidance to the development of high-performance biosensors for medical and environmental applications.