 The resonance states in ballistic open quantum systems form a clear chain structure, and this is reflected in the underlying classical dynamics of the three-disc system. Resonance states along one chain are correlated while those of different chains show an anti-correlation. The localization of these resonance states oscillates between different regions of the trapped set as one moves along the chains, and this modulation of resonance spacing is connected to the interaction of several periodic orbits. This article was authored by T. Weitsch, S. Barkofen, Yukul, and others.