Cellulose nanocrystals (CNC) and nanofibrils (CNF) were obtained by acid hydrolyzis and mechanical treatment, respectively, of cellulosic fibers from paper. Additionally, surface modification was performed for CNC by neutralization (NaOH) and oxidation (TEMPO). The thermal stability, surface properties and rheological behavior of these nanomaterials were compared. A clear difference in CNC surface was found upon neutralization and oxidation treatments, leading to distinct thermal behaviors. Optical and rheological properties were found to be predominantly by the particles size, being strongly affected by inertial effects.