The bark of Pinus radiata D. Don is recognized as a rich natural source of proanthocyanidins (PAs). Barks of Pinus radiata D. Don were extracted to produce a raw extract, and then purified to produce 4 fractions, with the aim of correlating its structural characteristics with the extract antioxidant capacity. The structural characterization was performed by acid catalysis in presence of phloroglucinol, foliowed by the detection of the components by High Precision Liquid Chromatography (HPLC). The subunits identified in the bark of Pinus radiata were: epicatechin- (4ß-2) - phloroglucinol (EC-P), catechin- (4á-2) - phloroglucinol (C-F) and (+) -catechin (C). The purified fractions showed different mean degree of polymerization (mDP), average molecular weight (aMW), concentration and reaction yield (R) with phloroglucinol. The concentration of total phenols decreased according to the order in which the fractions were eluted. All the fractions presented a high antiradical activity (evaluated as scavenging capacity of radical DPPH>). Nevertheless, the fraction FU presented the greatest tannin concentration and antioxidant activity. The structural characteristics of the extract of Pinus radiata D. Don bark could be correlated with the antioxidant activity of the extract.