Thanks for your reply. I added in my program gdcmImageIO->SetLoadPrivateTags(true); and indeed, the output generated dicom has more tags than before. However, some tags from the input dicom are still missing like 0008,1032 SQ (Sequence with undefined length). In itkGDCMImageIO.h, I only see functions to load sequences for GDCM 1.x. Is there any for GDCM 2.x ?