Lightning is a huge electrostatic discharge searching for a way down, and it isn’t particularly interested in whether or not it has been hit before. Taller objects, such as trees and skyscrapers, are usually choice targets because there is a shorter distance between that and the origin of the lightning. The tallest tree in a forest can get struck several times until the storm passes.

Source – http://www.iflscience.com/health-and-medicine/common-science-myths-most-people-believe/