  We derive an expression for the luminosity distance in a perturbed Friedmann
universe. We define the correlation function and the power spectrum of the
luminosity distance fluctuations and express them in terms of the initial
spectrum of the Bardeen potential. We present semi-analytical results for the
case of a pure CDM universe. We argue that the luminosity distance power
spectrum represents a new observational tool which can be used to determine
cosmological parameters. In addition, our results shed some light into the
debate whether second order small scale fluctuations can mimic an accelerating
universe.
