Enological tannins are widely used in winemaking process to improve different characteristics of wines. A wide spectrum of enological tannins is now available on the market; however, the tannins' chemical nature and botanical origin are not always clearly defined in the commercial products. The aim of this work was the chemical characterization of ten commercial plant-derived tanning agents of enological use. Enological tannins were analyzed by spectrophotometry (total phenols, total tannins and gelatin index) and high performance liquid chromatography (HPLC-DAD) (low molecular weight phenolic compounds). In general it was possible to observe important differences in the concentration of total phenols, total tannins and gelatin index values among the commercial products studied. By using HPLC-DAD it was possible to classify different types of tannins (mainly hydrolyzable (gallotannins and ellagitannins), condensed or proanthocyanidic tannins and blends of these groups). Clear differences were evident between the study results and the information on the type of tannin indicated on some of the commercial tannin labels. These discrepancies could lead to technological problems in the winery industry because of the different aims that guide the use of different types of these enological products.