This paper aims at presenting the usefulness of combining satellite optical data from the visible and infrared wavelengths with longer wavelength radar data for land cover mapping in Portugal. This is a ground-breaking study in a geographical region that does not experience continuous intraannual dreadful atmospheric contamination that commonly justifies radar usage. In this study we exploit the ability of ASAR images as an extra input feature for land cover classification together with the most used satellite optical data, i.e. Landsat. The goal of this paper is three-fold: 1) compare single date classification of ASAR data with Landsat data for land cover mapping; 2) evaluate the usefulness of multi-temporal ASAR measurements for land cover classification improvement; and 3) to compare a final map accuracy assessment with the classification scores attained with training and test sample sets. We conclude that ASAR imagery does not individually improve overall classification accuracy, but their synergy with Landsat data or in a multi-temporal context show up specific advantages; statistically sound accuracy assessment of final map bends optimal classification accuracies attained with test sampling observations.