This research was conducted to identify plant regulatory regions by gene tagging method. A promoterless GUS coding sequence was introduced to Populus nigra × P. maximowiczii via Agrobacterium strains(LBA4404/EHA101), and putative transgenic poplars were selected by culturing on medium containing G418(60㎎/ℓ) and by GUS assay. Among them one positive plant was to amplify the native sequences flanking to the introduced GUS gene in plant genome by inverse PCR method and from this 730 by DNA product was obtained. After subcloning and sequencing, it has 88% homology to the Eucalyptus gunnii CAD(cinnamyl alcohol dehydrogenase) gene. The GUS gene fused with the putative promoter reinserted into poplar leaves by particle bombardment method to test the funtional promoter activity. Upon staining with X-gluc, many blue sprots appeared on the leaf segments bombarded by the chimeric gene 2-3 days, thus the isolated DNA fragment contain some possible coding region as well as a putative regulatory sequences of poplar CAD gene.