We have used the recently completed soft X-ray spectromicroscopy facility at the Canadian Light Source (CLS) to study individual multi-walled carbon nanotubes (MWCNTs) with scanning transmission X-ray microscopy (STXM). Specifically, spatially resolved C 1s X-ray absorption linear dichroism signals were used to map structural defects. The STXM on CLS 10ID1 beamline is particularly powerful for such studies since its elliptically polarized undulator provides fully linearly polarized X-rays with their E-vector orientation continuously tunable from -90 to +90°. We correlate the magnitude of linear dichroism of the C 1s → π π* transition with the quality of the crystalline structure, in particular presence of sp defects. We show that the dichroic magnitude along a MWCNT can be used to map local defect density.