The aim of this paper is the probabilistic
representation of the probability density function (PDF) or the characteristic function (CF) in terms of fractional moments of complex order. It is shown that such complex moments are related to Riesz and complementary Riesz
integrals at the origin. By invoking the inverse Mellin transform theorem, the PDF or the CF is exactly evaluated in
integral form in terms of complex fractional moments. Discretization leads to the conclusion that with few fractional moments the whole PDF or CF may be restored.
Application to the pathological case of an -stable random variable is discussed in detail, showing the impressive capability to characterize random variables in terms of fractional moments.