This document describes a method and system for object localization. In accordance with the method an object (1) is illuminated by at least one first type of signal, and response of the signal is detected. In accordance with the invention the object (1) equipped with a transponder (2, 3) backscattering the first type of signal, the transponder (2, 3) is illuminated also by a second type of signal affecting to the backscattering frequency of the transponder (2, 3), and the backscattered signal from the transponder (2, 3) is detected in order to localize the object.