Semiconductor nanowires are widely used to interface living cells, and numerous nanowire-based devices have been developed to manipulate or sense cell behavior. We have, however, little knowledge on the nature of the cell-nanowire interface. Laminin is an extracellular matrix protein promoting cell attachment and growth. Here, we used a method based on fluorescence microscopy and measured the relative amount of laminin adsorbed on nanowires compared to flat surfaces. The amount of adsorbed laminin per surface area is up to 4 times higher on 55nm diameter gallium phosphide nanowires compared to the flat gallium phosphide surface between the nanowires. We show that this enhanced adsorption on nanowires cannot be attributed to electrostatic effects, nor to differences in surface chemistry, but possibly to pure geometrical effects, as increasing the nanowire diameter results in a decreased amount of adsorbed protein. The increased adsorption of laminin on nanowires may explain the exceptionally beneficial properties of nanowire substrates for cellular growth reported in the literature since laminin is often used as surface coating prior to cell cultures in order to promote cell growth, and also because primary cell suspensions contain endogenous laminin.