Using coupled 3D modelling of electrical, thermal, and optical processes, we consider operation of a blue LED with advanced thin‐film flip‐chip design. Significant effect of current crowing on light extraction from the LED die is predicted theoretically. As a result, the light extraction efficiency is found to decrease remarkably with the operation current. The nature of the effect is identified, and some ways for improvement of the high‐current extraction efficiency are suggested and examined by simulations. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)