In this paper we investigate the localization performance limits of massive arrays working at mm-wave frequencies and adopting two different beamforming strategies. In the first one, array weights are set in order to point towards a precise direction (classic beamforming), whereas in the second one, such weights are randomly chosen (random beamforming). Thanks to the large set of measurements as well as the high angular resolution provided by massive arrays, only one single anchor node can be used for localization estimation, thus avoiding over-sized infrastructures dedicated to positioning. Accounting for such beamforming strategies, performance is evaluated by taking into account the effects of arrays orientation and beamforming weights non-idealities arising when the number of antennas is high and low-complex components are adopted. Results show that classical beamforming outperforms the random one, but also reveal that the latter remains a feasible solution in all those applications requiring low complexity. © 2017 IEEE.