The invention describes a method of performing a structural inspection of a wind turbine rotor blade (2), comprising the steps of subjecting an area (20) of the rotor blade (2) to a thermal gradient; imaging the thermal field in that area (20) to obtain a number of thermal field images (M1, M2,..., Mn); and analysing the thermal field images (M1, M2,..., Mn) to detect a structural anomaly (H). The invention further describes a rotor blade structural inspection arrangement (1) for carrying out the inventive method.