Duckweeds, the fastest growing angiosperms, are gaining increasing attention with respect to their practical applications. Different clones of the same duckweed species vary in their physiological properties. Hence, screening of suitable clones of a species is very important. To enable the identification of clones, a clear taxonomic classification and barcoding at different taxonomic levels, i.e. genera, species, and clones is a pre-requisite. In the present project, we have focused on the genera Spirodela and Landoltia. Spirodela polyrhiza (L.) Schleid. (42 clones), Spirodela intermedia W. Koch (14 clones), and Landoltia punctata (G. Meyer) Les & Crawford (15 clones) were characterized using three plastidic sequences (rpl16, rps16, atpF-atpH) and AFLP fingerprinting. Genome size determination showed significant differences between the two genera. The genetic variability is lowest in S. polyrhiza and highest in S. intermedia. Although the resolution of phenetic variability by AFLP fingerprinting is much higher than the sequence variation of the selected plastidic regions, not all clones could be identified unequivocally. However, without any exception, all clones were strictly categorized into the three species as defined by the morphological markers. The results do not justify the separation of some clones as Spirodela biperforata from S. intermedia. Keywords AFLP fingerprinting * Structure * Duckweed * Lemnaceae * Barcoding * Spirodela * Landoltia