The nanostructures of co-sputtered Pt/C layers were investigated by anomalous small-angle X-ray scattering (ASAXS) experiments with synchrotron radiation. The ASAXS method permits us to separate the platinum-scattering contribution from the carbon background and thus opens up the possibility to retrieve nanostructures formed by the Pt atoms. To obtain the structural information from the scattering data, a columnar structure model is proposed and applied to three different samples prepared with different platinum sputter targets. The results are compared to those obtained from cyclic voltammetry.