Clouds reflect solar light much more strongly than aerosol particles. Therefore, the retrieval of aerosol optical depth is usually only attempted over cloud-free areas. A very strict cloud detection scheme has to be applied to remove all cloudy pixels. However, often not all clouds are detected. To remove possibly cloud-contaminated pixels, a cloud post-processing algorithm has been designed, which effectively solves the problem and results in smoother AOD maps and improved validation results.