The formation and photoluminescence (PL) of InP nanowires grown by metal organic vapour phase epitaxy on InP(111)B substrates, using colloidal gold nanoparticles as catalysts, are investigated. The dependence of the orientation and dimensions of the nanowires on the growth temperature is studied using scanning electron microscopy. Vertically aligned [Formula: see text] oriented nanowires with a mean base diameter in the range 50-150 nm, and a tip diameter of 50 nm, show a PL blue-shift of about 80 meV compared to the substrate. Blue-shift due to quantum confinement is ruled out because of the large diameter of the nanowires. A clear correlation between the orientation of the nanowires on the substrate and the PL peak position is observed. Based on x-ray diffraction and transmission electron microscopy measurements, it is proposed that the as-grown vertically oriented nanowires have crystallized in the wurtzite lattice instead of in the zinc-blende structure, which results in a blue-shifted PL.