Carbon nanospheres (∅∼50nm) prepared by chemical vapor deposition exhibit Curie-type paramagnetism, with a localized spin density N S =4.01×10 19 spins/g. The spheres are solid, as shown by their cross-sections. Their low surface area excludes the presence of exposed graphene layers at the surface being the origin of paramagnetic centers. Inside the carbon spheres, HRTEM reveals a concentric wavy pattern of graphitic (sp 2 -bonded) clusters (size<2nm) embedded in disordered carbon. The high density of carbon atoms with sp 2 –sp 3 hybrid orbitals acting as paramagnetic centers, at interfaces between graphitic (sp 2 -bonded carbon) clusters and amorphous carbon, can explain the magnetic measurements.