Two Cosmo-SkyMed observations of the inundation occurred in Myanmar on May 2008 are analyzed in this paper to study the potentiality of this sensor for flood mapping . The first image is temporally close to the peak of the event, while the other one was acquired one week later. Our study accounts for the physics of the radar return in the presence of water surfaces. In particular, both specular reflection, typical of open water, and double bounce backscattering, typical of forested and urban areas, are considered. From the analysis of the Cosmo-SkyMed images, a map representing the extension of the flood at the time of the first radar acquisition is derived.