A hierarchical version of the particle swarm optimization method called H-PSO is introduced. In H-PSO the particles are arranged in a dynamic hierarchy that is used to define a neighborhood structure. Depending on the quality of their so far best found solution the particles move up or down the hierarchy so that good particles have a higher influence on the swarm. Moreover, the hierarchy is used to define different search properties for the particles. Several variants of H-PSO are compared experimentally with variants of the standard PSO.