We report a systematic study of the synthesis of multiwall carbon nanotubes (MWCNTs) by arc‐discharge in liquid nitrogen (LN2). The effect of the variation of the experimental parameters, such as size of electrodes and discharge current, on the formation of nanostructures has been investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. We found that an increase in the electrode size and/or in the discharge current determines a better quality of the nanotubes, as shown by the reduction of the ID/IG ratio in the Raman spectra. In some experimental conditions radial breathing modes (RBMs) have been observed and attributed to nanotubes with small innermost tube diameters.