  Quantum states extended over a large volume in phase space have oscillations
from quantum interferences in their Wigner distribution on scales smaller than
$\hbar$ [W.H. Zurek, Nature {\bf 412}, 712 (2001)]. We investigate the
influence of those sub-Planck scale structures on the sensitivity to an
external perturbation of the state's time evolution. While we do find an
accelerated decay of the Loschmidt Echo for an extended state in comparison to
a localized wavepacket, the acceleration is described entirely by the classical
Lyapunov exponent and hence cannot originate from quantum interference.
