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The growth modes of NO on Ni{111} have been determined using a novel LEED technique. Measurement of LEED intensities at the superstructure beam positions as a function of coverage indicate that initial adsorption occurs randomly up to a coverage of 0.25 ML. After this point islanding occurs until the c(4×2) half-monolayer coverage is reached. Diffuse LEED I(V) analysis has also been used to determined the structure of a low coverage phase. This low coverage phase gives rise to an optimum structure consisting of 70% fcc and 30% hcp threefold hollow site occupation, which contains a large buckling of the first nickel layer. This contrasts with the optimum structure for the ordered, 0.5 ML c(4×2) phase where a 50/50 mix of fcc and hcp site occupation is determined and no buckling is found. These site assignments do not agree with assignments made using vibrational spectroscopy. Our results provide the basis for a new interpretation of the vibrational data allowing us to give a complete picture for the adsorption of NO on Ni{111} at low temperatures.