We discuss in this chapter the salient issues related to lightning protection of large wind turbine blades. Lightning protection of modern wind turbines presents a number of new challenges due to the geometrical, electrical and mechanical particularities of turbines. Wind turbines are high structures and, like tall towers, they not only attract downward flashes but initiate upward flashes as well. The proportion between these types of flashes depends on many factors such as the structure height and the local terrain elevation. The rotation of the blades may also trigger lightning and result in considerable increase in the number of strikes to a wind turbine unit. Since wind turbines are tall structures, the lightning currents that are injected by return strokes into the turbines will be affected by reflections at the top, at the bottom, and at the junction of the blades with the static base of the turbine. This is of capital importance when calculating the protection of internal circuitry that may be affected by magnetically induced electromotive forces that depend directly on the characteristics of the current in the turbine. The presence of carbon reinforced plastics (CRP) in the blades introduces a new set of problems to be dealt with in the design of the turbines’ lightning protection system. One problem is the mechanical stresses resulting from the energy dissipation in CRP laminates due to the circulation of eddy currents. The thus dissipated energy is evaluated and recommendations are given as to the number of down conductors and their orientation with respect to the CRP laminates so that the dissipated energy is minimized. It is also emphasized that the high static fields under thunderclouds might have an influence on the moving carbon fiber parts. Representative full scale blade tests are still complex since lightning currents from an impulse current generator are conditioned to the electrical characteristics of the element under test and return paths. It is therefore desirable to complement laboratory tests with theoretical and computer modeling for the estimation of fields, currents, and voltages within the blades.